Minis with a passive skill means that they have the specified effect at all times.
Clash Skill
Clash abilities activate at the start of the round.
Boast Skill
Activates when the Mini defeats an enemy.
Super Skill
An ability that the Mini can activate during battle once they have full energy.
K.O. Skill
Activates when the Mini with this skill is defeated.
How to Choose Star Ability in Battles
Every mini in the game has 4 abilities, but you need to unlock them outside of battle by getting more copies of them through rewards or buying from the shop. However, these abilities are only available during battle once you give them more stars by putting duplicates of the mini on the board.
If you simply put a duplicate of a mini on the field, they will automatically unlock the first star skill, but you can choose which skill to get first by tapping the mini and selecting it before putting it on the board.
Selling Minis During Battle
If you already have a unit placed on the field, you can drag them into the Elixir pot to "sell" them and get a refund on the Elixir cost. This lets you quickly change your team setup if you need to do so.
Special Tiles
There are multiple maps in Clash Mini, and each different map, other than the first one, has 1 special tile for both you and your opponent. Placing a Hero/Mini on these tiles will activate certain effects during battle at the start of the round.
Each round, the special tiles will also move to different places. If they're on the back, it will benefit units that are ranged type, while near the center can be good for tanks or bruiser type units.
Keep in mind that your opponent also has these special tiles, though, they appear in a random tile that's not related to yours. This means that you have to consider how to not get countered.
Healing Star
Units placed on this tile will be healed 2 HP for 4 seconds.
This is often best used for tanky units with a lot of HP so that they can survive and properly take advantage of the heal.
This is counterable with units like the Prince that can knockback and stun them to deal with tanks, or Fisherman to pull them towards your team.
Magic Mirror
Units placed on this tile will be duplicated, appearing next to the unit or to the closest tile, but the clone will only have 20% HP.
Compared to the Supercharger tile, this helps Minis with clash abilities. Due to the low HP clone, tanks aren't really the best option even though they can help take a few hits. Most units can take advantage of this pretty easily, it just depends on where this tile is placed.
You can sort of "control/change" where the clone spawns by surrounding the unit placed on the tile with other units. This can end up making the clone appear on the closest tile, which can be in front, or behind the unit placed on the tile.
If it's in the front:
Any unit with a clash effect can be good, like Spear Goblin, Fisherman, Prince, or Bowler to get double of their effects at the start.
Giant Skeleton is a good option since it has a KO ability that can deal damage. A low HP clone will mean that it will activate faster.
Miner is a decent option since both of them will go to the back, potentially not taking any attention from the enemies and be able to take out some rangers or healers before going down.
If it's in the back:
Archer Queen or any ranged Minis can be pretty good since they are more easily protected, allowing them to continuously deal damage, but potentially counterable by an enemy's Miner.
Supercharger
A unit placed on this tile will get +3 energy at the start of the round.
This is mainly for units that have a super ability, otherwise, it does nothing. Similar to the Magic Mirror tile, what unit to place here also depends on where it is on the map.
Wave Master is almost always good on this tile since his super lets him move around the map, stunning multiple enemies if hit. Having this available early can change the battle entirely.
Clash abilities like from Bowler, Spear Goblin, Fisherman, or Prince are your counter options to deal with your opponent's supercharger tile.
Bounce Seashell
At the start of the round, a unit placed on this tile will be bounced into the opposite side of the board.
This effect can essentially make any of your unit into something like a Miner that can jump and go after the enemy's backline, which will also mean that you'll have to play around this and not focus on a lot of rangers.
Keep in mind not to put any Mini that has a clash ability on this tile since they will get bounced right away before they get to use their clash ability.
Units that can be good for this tile:
Heroes like Shield Maiden or Wave Master have enough HP to survive until they get their super so they can cause some disruption on the map.
Giant Skeleton or Valkyrie can be good if the bounce tile is in the center so that you get to fully utilize their area of effects.
At the start of the round, a unit placed on this tile will have a buff effect that will revive it once, giving it 6 HP if it gets KO'ed.
During the revive animation, the unit can't attack or be attacked. The unit revived will also resume attacking its last target if available, instead of changing to the nearest unit.
Trying Out All Units
This game has Daily, Weekly, and Mini quests that give rewards like Carrots or Golds to help you progress, and the earlier you finish them, the sooner you'll get those rewards.
Daily and Weekly quests refresh after a certain time, but there are only a certain amount of Mini quests available. Once you finish all the Mini quests for the ones you own, it's time to change your Minis around so you can pick up the rest for faster progression.
If you are already high level and don't want to use your low level Minis to go against high level opponents, you can switch to casual mode instead by tapping on the "game modes" button next to the duel button.
In Rumble, you will only get the "win" if you become the champion, which is more difficult to do compared to Duel. So if you only want to do this for the missions, then it's faster to do Duels instead.
When selecting your units to change your team, you can see which Minis you still have quests for, as shown above by the mission icon on their top right. In this example, Spear Goblin no longer has any more Mini missions, but there are still missions for both the Knight and Archer.