⭐ Merge or not: the 4 kinds of cards

Merging always looks right: the card ranks up and gets stronger. But merging also takes a Minion off the board. In some decks that costs nothing, in others it costs the game. Here's how to decide.

What the game says

officialYou can merge 2 Minions of the same ★ rank up to a maximum of 3★.

officialThe Minions' ATK will be added together when they merge.

officialGreen numbers in ability descriptions mean they change with your Minion's ★ rank.

officialMerging Minions is the best way to improve your ATK.

officialAbility texts show 4 numbers (like 2/4/8/20) because Rumble Chess allows merging up to ★4 (in-game wiki). In the normal mode the first 3 apply.

The math nobody does

inferenceSince both copies' ATK is added together on merge, you lose no ATK by merging. Two things change:

confirmedEvery Minion on board sends Rush Squad units to the opponent's side, temporary ones included. Fewer bodies, fewer units.

The 4 kinds of cards

Reading each card's text, they fall into 4 groups. The site's deck builder uses this same split.

1. Wide: no need to merge

officialHeadless Jack "Aura: This Minion gains ATK +5/10/20/60 for every 10% HP the Captain is missing." Each copy has its own aura, so 2 ★1 copies give +5 and +5, same as one ★2.

officialPom Piper "Ready: Temp increases 3 random Minions' ATK by 2/4/8/20." Two ★1 give 6 buffs of +2; one ★2 gives 3 buffs of +4. Same total, spread over more Minions.

other

other

other

★2

★2

★2

other

other

other

other

other

other

inferenceBoth boards have the same Headless Jack power. The 6-copy board wins on bodies; the ★2 board wins 3 tiles. What decides it is what you'd put in those 3 tiles: if nothing better, wide wins.

communityReal example seen in a high level game: 7 unmerged ★1 Headless Jacks, with the Captain kept at low HP on purpose to max out the aura.

2. Tall: only good merged

officialGuaca Sage "Ready: Temp increases this Minion's ATK by 80%/80%/80%/120% if it's at 3★." Before ★3 the ability does nothing. Merging is the whole plan here.

officialGlowkeeper "When this Minion is promoted, all other Minions' ATK increases by 2." The bonus only comes when it ranks up. Without merging, it delivers nothing.

3. Unique: the 2nd copy hurts

officialShamaness "Ready: Increases the ATK of other Minions by +2/4/8/32 (only 1 of each duplicate). Instead grants ATK +4/8/16/64 if there are no duplicates on the field." Duplicates on board halve the bonus. With her, the whole deck prefers merging.

officialJoe Tycoon "Deploy: Increases the selected Minion's ATK by 8 and spends all Suncoins, each increasing its ATK by 2." A second Joe in the same round finds an empty pocket.

confirmedNext round, with fresh sun, another Joe is worth it again.

4. Capped: good up to a point

officialCheerbloom "Aura: Increases the ATK of the Minion 1 tile above by 2/4/8/20." Each copy needs a Minion above it, so the board itself limits how many pay off.

officialSeed Peon "Reduces the Purchase Price by 2. Temp increases the Purchase Price by 1 for each Seed Peon you buy." Each copy bought in the same round costs more. The exact number of copies where it stops paying off hasn't been measured yet.

When to merge even in a wide deck

inferenceYou ran out of tiles. With all 9 taken, the next copy only goes in by merging.

communityThe round before the Boss (2, 5, 8). The Boss swallows Rush Squad units to gain HP; fewer bodies can keep it leaner. See the Boss rounds guide.

Carrot Broker Bug reported by Khaan in game: if you buy a card straight from the shop onto another copy (merging), its on-entry effect (On Purchase) doesn't trigger. With Carrot Broker that loses you the guaranteed cost 8. Buy it into an empty tile and merge after.

Quick summary

The deck builder builds the target board with how many copies of each card to use and says, card by card, whether to merge. See also Boss rounds.