Here's everything you need to know before playing Dot Arena on Android or iOs.
1. Starting out (Lv 1 - 32)
1. Starting out (Lv 1 - 32)
You will be able to start campaigning and get 5 free heroes. They are Captain, Noire, Ember from treasure chest, Kane and Eva from quest completion. At the start it is recommended to fuse all of them as they are your only units and they will bring you to further maps. This phase is a smooth and relaxing, upgrading and farming what you need is sufficient
Important: The first golden chest of 288 diamond is a guaranteed 3* hero. Save up for it and use your diamond on it! Also you get to open one free golden chest every 48 hours so don't forget!
1.1 Starter heroes quick Evaluation
Captain
Pro: 1 small AoE stun and single target lift
Con: Not as tanky as the other front liner, 3rd and 4th skills are average only.
Note: His stun and lift success rate scale with ability level. However normally I wouldn't even upgrade this unit as I would rather spend the ability point on other heroes for more damage.
Rating: 1/5
Noire
Pro: AoE silence as third ability, excellent for all case. Superb fourth skill which increase the entire party physical attack.
Con: First and second skill are decent but pale in comparison to the top tier units.
Note: Silence success scale with ability level and is important to level for it to be effective. Possibly the best starter as it really turns out to be a huge damage contributor to the team with a silence that help in PvP.
Rating: 4.5/5
Golden tip: Completing heroic quests will eventually give you 20 ss of noire, enough to make her 2* 
Ember
Pro: Extremely strong early and mid game (before level 50)
Con: Suck real bad after due to 4th skill that is not of much use when the rest of units get really good attacks.
Note: Third skill stun success rate scales with ability level. Useful for starter but think twice if you really want to invest a lot on it.
Rating: 2.5/5
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Kane
Pro: Consistently above average through the game, after getting his 4th skill his damage is boosted greatly
Con: Only 1 interruption skill and a lot of better mage out there
Note: Third skill success rate of canceling opponent skill scales with ability lv. Decent mage but don't have disables to help you win your PvP. Kane can be upgraded to purple at lv 49 (2-4 level earlier than most which can help you a lot)
Rating: 3/5
Eva
Pro: Only healer and a charm skill
Con: Doesn't do much damage but its fine 
Note: Charm success rate scales with ability level. Only healer available and relatively ez to farm. Charm can be an awesome help if the charmed opponent cast skill on its own team xD
Rating: 5/5
<General Knowledge>
1. Ability points are unlock at level 8, you can start leveling them when your reach level 8.
2. Ability level can be raise to heroes level at max. Eg, lv 10 captain can have its skill at lv 10 at best only.
3. Ability point recharge at 1 per 5 min and you can keep 10 maximum at vip0.
4. Your heroes get stats when you fuse them, they can progress from white -> green -> green+1 -> blue -> blue+1 -> blue+2 -> purple and so on.
5. Upon fusion to green, blue and purple, your hero unlock a new ability.
1.2 Arena
Unlocks at level 10. You earn diamonds when you improve your highest ranking attained. You can check it @ Arena -> Rules. Diamonds given increase exponentially as your climb higher rank. Meaning to say, the diamond u get from Rank 200 -> Rank 100 is way more then Rank 1000 -> Rank 900.
Important: Save your dragonscale and arena point for heroes. Also you can refresh the shop for 10 arena chips (so if you have 1010 chips you can buy a hero twice!)
Rationale: These heroes are the easiest to get 5* as you can consistently get 5 ss from each exchange. If you are free to play, it is highly likely that these heroes will be your first 5*. Don't waste them on equipment as the benefits of getting 5* hero is a lot more rewarding.
Golden tip: The arena reward are given out daily at 9pm (GM+8), leave your last arena chance and refresh to a winnable opponent, 30 seconds before 9pm, attack and hope to win! If you win you secure a higher ranking for more rewards!
1.3 Arena heroes quick evaluation
Bo&Mo
Pro: Very high crowd control and damage
Con: Get hits pretty often due to position
Rating: 4.5 / 5 One of the best crowd control and good damage dealer
Ragnar
Pro: High damage and AoE damage on death
Con: No crowd control and squishy
Rating: 2.5/5
Vincent
Pro: Awesome shielding, healing and damage. Superb aura that boost entire team magic resistance
Con: Lower hp and phy arm then other tanks, get worst at mid-late game
Rating: 4.5/5 -> 2/5?
1.4 Cavern of time
Unlocks at lv 14. Nothing much to say here, make sure you complete them daily for exp/$
1.5 Dojo training
Unlocks at lv 16. Complete them for fragment which takes lots of energy to harvest.
Valley of broken halberd: You need a magic atk team
Cursed City: You need a physical atk team
Ride of the Valkyries: You need ladies (bleh lol)
Golden Tip: Strive to win the normal difficulty of Ride of the Valkyrie as it drops 2-3 ultimate orb fragment which equates to 10 battles of farming drop (60 energy!). It is tough as you as only use female, if you can hire mercenary from your guild that can help you to win, do it!
For those without a 4th female, I tried and won easy mode on lv35 and normal mode on lv46 with the 3 females starter, so fred not! but for higher difficulty, you MUST have more females
1.6 Trader
Unlock upon completion of Chapter 2 normal campaign.
Golden Tips: Visit Trader at the 4 timings - 9am 12pm 6pm 9pm
Buy all the gears and fragments. You can choose to buy the hero soulstone (ss) if it is the hero you wish to build.
Rationale: 1 Purple fragment takes about 5 battles to obtain, which equate to 30 food saved! Buying a boots of speed, can equate to 1-3 battles saved. You would want to spend food on clearing stages and farming specific and desired gears, hence whatever you can obtain through trader is a must buy! If you have no use for these gears, they can become precious enchantment pieces.
2. Mid Game (Lv32 - 50)
This is where the fun and strategic part of the game starts to kick in, with lots of decision to be made and a drought of lv 44-50 whereby you cannot equip any new equipment (for most heroes). In this period, spend most of your energy farming purple fragments, like ultimate orb / mystic staff as you need many of them for fusing (especially ultimate orb). 10 runs give about 2 fragment and it takes 20 fragments to complete 1 purple gear.. If you do the math, it is 100 runs -> 600 energy worth!, now you understand why you must buy from trader and also start early, before you can equip them.
2.1 Goblin Peddler and Black Market
Unlocks at completion of Chapter2, lv 30 and 40 respectively. Goblin Peddler and Black Market are similar to trader but offer better items (and more expensive of course). They appear randomly when you spend food.
Golden Tips: Always keep about 50-100k on hand once you unlock Goblin Peddler
Rationale: Same as trader, but the merchant offer better gears and are more costly. You don't want to regret not being able to buy them when you encounter them since they last 1 hour only.
2.2 Guild
Unlock at lv 32. Other then being part of a community in game and awaiting for future patches for more functionality, there are still a couple of things that help you. 1, you can give props to a higher level player for free for 15 energy 2, you can hire and dispatch heroes to mercenary camp that can earn a tiny weeny bit of money. Hiring mercenary cost money so don't spend unless you are sure the earning outweigh the cost.
2.3 Crucible of Fire
Unlocks at lv 32. One of the best gold farming activity. You can use your entire arsenal of heroes to clear the stages and there are a total of 15 stages. Hp and Power are carried over battles to battles and died heroes cannot be revived. Difficulty of stages increase along the way and it is random who and what heroes you fight. Dragon scales can be earned and used for exchange, use them for heroes solely! Crucible of fire will get a lot more difficult as you level up. This is because you can start facing opponent with higher level then you at about the 10th stage. When you are nearing lv 50, you get to fight heroes that have purple fusion and you are not even there yet! Thus proper planning and strategy have to be in place to make sure you progress to the furthest with you can be.
Golden tip: Do crucible later in of the day after you have gain some exp/lvl or equipped with better gears. This little boost might win u an extra battle!
Also, if you clear CoF you get 1300 scales, you can refresh the shop for 10 scales and buy your choice of hero twice if you want. Example: Buy jugo = 500 scale, refresh shop = 10 scale, buy jugo again = 500 scale. Hence in 2 days, you get 2600 scales > 500 + 10(1st reset) + 500 + 500 (day 2) + 10(1st reset) + 500 + 10(2nd reset) + 500 meaning you can get 25 SS in 2 days!!!!
A good crucible team can
1. Deal as much damage as possible (High DPS)
2. Taking as little as possible within a short time (Disables and healing)
3. Use the least possible power possible (Sustain)
4. Keep power bar high at every star of battle (Sustain)
Golden tip***: If you have more than 5 strong heroes, bring your spares the first few battle of crucible where it is easiler to win. Make and keep their power bar full. Should your main team lose, you can bring in your weaker units that have skills ready to be activated to blast at your opponent straight away! This strategy always allow me to clear a couple of stages more. Imagine you have 10 heroes and 5 spare heroes with power max, ready to blast when sent in.
Further explanation, for example you have a main team (take it as all level 40) of
Captain
Bo&Mo
Kane
Eva
Hydral
with spares (Level 35 minimum, they ought to be cause you would level them for treasure hunt)
Ember
Noire
Jugo
If you start crucible you would face off lower level enemy maybe lv 30 for first stage. Team up Ember, Noire, Jugo with Captain + BoMo and clear stage 1/2 without using any skills, this will keep all power bar full. First few stages are relatively easy, you will be able to win just by putting a few main team heroes in. Once the spares power bar is full, you can take them out and use your main team and fight through crucible. As example, lets say your main team got wiped at stage 10, you could bring in ember+noire+jugo and activated their skill to do a burst of damage. This could actually help you clear that 1 stage more
1 Example with pictures below! From the first picture, you see that I actually made all my usable spare heroes's power bar full (their ability point and equipment are not at their best). My main 5 is Hydral + Windrunner (rented, 6 levels lower then me lol) + Kane + Voo + Lucas. After some of my main team heroes died, I filled up with spares and was able to last 1-2 more battles. In the upcoming battle, if you see the result, in the second picture below, my Ragnar did 14,638 and Noire did 13,020 damage. All this was not possible if I had not charge their power bar at the initial stages of Crucible, ready to blast and activate the moment they go into battle.
In my opinion, it is very effective to bring in 2 heroes with all-target spell burst, 1 healer,1 hero that can interrupt opponent entire team casting (super crucial) and 1 solid tanker. Its a huge bonus if your heroes that do AoE can interrupt as well (jade). You could blast opponent team 2 times, their power bar will be full, cast your interrupting skills and their team will be at 0 power bar xD Because of the difference in animation, you might not get to interrupt all your opponent, in this case, choose to target at their most lethal heroes (luna, windrunner, aoe disablers etc).
After trying out a few heroes, I find Vincent the best tank by far because of its healing and immune abilities and Jade the best mage (huge damage + all target skill interrupt) . In addition I don't find bring 2 tanks effective because you lose out on a lot of damage output, unless your offense tank really pack a huge punch and is not in front of your meaty tank.
Continued at part 5.1, some VERY useful tips there! (use ctrl-f for 5.1 xD)
2.4 Crucible heroes quick evaluation
Hyral
Pro: All skills are very good especial 4th which increase team magic attack
Con: Takes very long to channel his 1st skill but it is rewarding if pulled off
Rating: 4.5/5 (Pick him if you have a magic team!)
Pro: Cast a lot more often than other heroes and damage the mid and back line more
Con: Jugo and Hydral are more worthwhile to get
Rating: 3/5
Jugo
Pro: 1st skill increase the entire party attack speed and damage (which means less time need to cast 2nd/3rd skill!) and especially good with physical damage team. V strong later game
Con: Weak early game
Rating: 3/5 -> 5/5
2.5 Treasure Cave
Unlocks at lv 42. You will be able to hunt for treasure/exp/diamond mines and harvest these from the mine for up to a fix amount. You can dispatch up to 5 heroes to mine at the maximum rate. Note: If you send your hero to mercenary camp, they can not be used to mine. Also only heroes which at least level 35 can be dispatched to mine. You can only have 2 mine at any point of time unless you are vip5. Hence it is advisable to have at least 12 heroes, 2 for mercenary camp and 10 for mines. Do note that people can attack and steal your mine, so log in periodically to check if you can.
3. Team Building Strategy and Game Battle (mainly for crucible, highly recommended to read 6.3)
This is an important aspect of game which I felt most player does not put much thought into. Not all heroes go well with each other, some has good synergy with others. So you have to plan what to focus on as you won't have the resources to upgrade every single ability and fuse every single hero you get. The bigger difference between arena and crucible of fire, is that crucible of fire involve sustaining for multiple battle while arena is all among bursting down opponent team as soon as possible. Hence, normally an arena team doesn't consist of a healer while crucible team require one.
Arena tip for team building: Know the fact both team starts with 0 power bar, do plan for your team for disable at different row. For example Silencer and BoMo get hit roughly the same and they tend to cast their s1 together, you won't want to freeze + silence as it is diminishing each other effect! Another example is using Noire and Ember, their silence + Stun together are not necessary! These are some consideration when planning your team!
3.1 Key Pointers you must know in a fight
1- Some skills can interrupt opponent skill.
This so important as if you can time your casting properly, you can cancel opponent skill and prevent tons of incoming damage which is vital for crucible of fire stages. Not only so, you must know your opponent sequence of casting, so that you know when you won't be stopped from casting. Common interruption skills are Ember, Eva, Kane, Noire third skill for example. Also, a critical physical or magical hit can interrupt casting as well!
Example of how timely casting can win a fight, imagine 2 teams of the 5 starters fighting each other. On the third turn, Ember Eva Kane and Noire are gonna cast their skill. If you time the casting of Captain perfectly, shipwreck hits opponent Captain, Kane and Ember while the red circle is shown, you stopped 3 skill attacks from the opponent team which is enough for you to win the fight on a equal setting!
An example in the picture below, I activated my hydral and started channeling, somewhere 3.5-4s after activation, I casted BoMo's 1s to freeze opponent. As you can see in the picture, I successfully interrupted Lumina's Esclipe (you see the moon but my party hp is full) and Medusa's glare. I then follow up with Statik 1s to finish them off
Also take note that if your second skill is in the midst of casting animation and you activate your 1st skill, you will cancel your second skill which lead to damage wastage! Learn to cast smartly both offensively and defensively!
2- Damaging your enemy too much energy without the capability to finish them off, will allow them to proc and cast their first skill on you for enormous damage. This is related to the first point, whereby you have to time your skill cast to interrupt opponent skill cast. Using the same scenario as above, but assume you are on the second battle of crucible of fire and had already had full power on your team from the start of battle. After the second turn (all second ability casted), you activated Noire and Kane's skill which dealt enormous damage on opponent's team. This will fill their energy bar and cause they to cast their first skill. If you time captain's shipwreck nicely, you be able to stop opponent's Captain, Kane and Ember from casting their primary skill on you. Another common example is when you use ember skill and it doesn't finish off opponent, opponent will then react with their first skill most of the time, you dont want that! So many sure when you use ember skill, you either finish off the opponent or have a disable ready to come after it!
These 2 pointers are essential and vital to maximizing your team potential and take time and practice. You have to understand opponent heroes's skill cast sequence and which of your team can be used to interrupt opponent.
3- Learn to bring the right hero.
If you see opponent having a physical team, bring a tank that has the best physical defense, likewise for the other. If you think opponent has lot of crowd control, bring someone that is able to interrupt them. All this take practice, knowledge and also the luxury of having multiple heroes which will all come with time
3.2 Focusing your resources and picking your heroes
This is especially important when you get more then 5 heroes. For a start decide if a physical or magical team suits your team? If Noire is in your main team and you have 3 mage, it be a waste of Noire's 4th skill which boost the entire team physical attack!
In my opinion, magical team is a stronger for a few reasons.
1- More heroes have 4th skill that boost physical defense, few has 4th skill that boost magical defense of the team
2- Magic attacker tend to fill their power a lot faster and is important for crucible as casting faster helps a lot
After lv 54, Physical teams can overtake magic team! 1 main reason is that physical attacker gets to equip tank item along the way and they are more tanky than mage!! I have a lv 59 account and is still able to clear 13-15 stages of crucible with a mage team, but it is tough! I tried a physical team on my alternate and it is showing decent results as well. So regardless, plan you teams. Be it physical or magical its all usable and you eventually need both for campaigns as well! 
However if your team composition is leaning towards a physical team, there is no point trying to force a magic team out as it will definitely be weaker  Do take note that it is recommended to have 1 healer and 1 tanker, hence you have to fill 3 damage dealers. As pointed out in section 3.1, it is very important to have heroes that have skill that interrupt opponent upon activation. Example of such heroes are Captain (animination takes time and does not cast on the entire team though), Silencer (full aoe), Windrunner (full aoe), Bo&Mo (full Aoe), Earthshaker (full aoe).
Assuming you do not pay for any heroes, this is some good team composition I can come up with (includes arena and crucible hero)
Magical Team
Captain (Tank with 1st and 2nd skill Crowd Control)
Hydral (Blind & AoE damage 3rd skill, a huge 1st skill damage and 4th skill that add magical attack to whole team)
Eva (Healer that benefit from Hydral's 4th skill)
Bo&Mo (1st skill CC with good damage from 2-4th skill)
Kane (3rd skill single target CC with final skill adding more magical attack)
Physical Team
Captain
Jugo
Eva
Noire (3rd skill mini aoe silence and 4th skill that add the entire team physical attack)
Ragnar
If you have extra heroes, feel free to play around and swap. Its easy to build a team, just make sure you choose the main 5 and level their ability to the max so that your main team is strong 
Note: After lv 50, a pure team isn't enough, you need spare heroes which are almost as strong as your main. Vincent will start to suck too.
4. Misc Tips
1. Clear all your daily task
This is the most important task, because it offers you a lot of bonus exp. At later stages, it takes very long to level up, hence every tiny bit of exp is important!
Rationale: Imagine 100exp for a task, it represent 100 food worth of exp which equates to about 16 campaign battle exp. It is really a lot and must not be missed daily
2. Do not spend excessive energy on soulstone of heroes that you probably won't use or aren't good, plan! This is important as you need a lot of gear at lv 51 - 53 fusion, you want to be able to fuse into purple right away when you hit that level, so do not neglect gear farming!
3. Always learn to spend energy and resources the most efficient way, keep this at the back of you head! For example, it is easier to get boot of speed from Ch1 then Ch6, don't waste energy there!
4. You don't have to upgrade every single abilities on your main team! For example Eva's second skill, Embers 4th skill can be placed lowest priority. Always evaluate which ability is more important to spend $ on.
5. Not all heroes's SS can be farmed easily, it is more advisable to find those heroes which have multiple stages for you to farm daily.
6. If you don't need a heroes, don't summon it! Because if you get a full hero from chest, it is more advantageous as a full hero is worth more SS!
7. Heroic stages that drop purple fragment is a very good spot to spend your energy as it can get you 1-2 fragment per 3 runs (36 energy with a shot at SS) whereas 10 runes on a normal stage gets you 2-3 (2 fragment mostly for 60 energy). Chapter 6 Beach encounter drop medusa ss and ultimate orb, a very good place!
8. You gain about 800 exp from daily task and 360 exp from food usage. Once your exp required hits about 2400, you might need a bit more then 2 days to level up. Many players will be tempted to use diamond for energy, however for the many levels to come, are you gonna spend diamond everyday as you be that tiny bit off to level?? Don't even start if you are not intending to spent diamond for energy in the long run!
9. To be honest, I prefer building a team for crucible over an arena team, as crucible give more reward imo and it is too tough to compete in arena with other players (some can even 5* their entire team in 2 weeks >.>"""). Some heroes that are useful for crucible but not so much in arena are Vincent, Statik, Gabriel and Healers.
10. You probably don't have enough resources to excel in arena, crucible and raid. You have to choose something to excel in first! At lv 40s+ you will start having the luxury to train more than 5 heroes as you already maxed them
11. Join a guild with many people (top spenders :P) as you can hire very strong heroes for your crucible run, make sure you are at the level to be able to use their heroes though.
Proceed to Part 2 of this guide.