At the end of each Act, one of three Bosses for an act will be encountered. The boss fight is denoted in the map by a big icon at the very top. Each boss has its own icon, so the player can plan their strategy in advance. The preceding map location will always be a Rest Site, allowing the player to heal before the fight. (The only exception to this is the Corrupt Heart in Act 4, which has an Elite encounter before it.)

Each boss slain adds 50 points to the run's Score. Slaying a boss without taking damage (not including self-damage cards such as Offering, Hemokinesis, etc.) adds an additional 50 points, and perfecting 3 bosses adds a 200 point bonus, overriding previous flawless bonuses.

After defeating the Act 1 and Act 2 bosses, the player will be rewarded with Gold, a potential random Potion, a choice between 3 Rare cards, and a choice between 3 Boss Relics.

On Ascension 20, the player will fight two different bosses consecutively at the end of Act 3.

Some relics will activate during boss fights: Pantograph will heal the player for 25 HP at the start of each boss combat, and Slaver's Collar will give the player an additional Energy at the start of their turn during boss (and Elite) combats.

In the Mind Bloom Event in Act 3, choosing [I Am War] starts a fight with a random Act 1 boss for a random rare relic. This boss fight does not count for the Score bonuses, but does activate the Pantograph and Slaver's Collar relics.

Act 1[edit | edit source]

One of these bosses will appear on floor 16.

Act 2[edit | edit source]

One of these bosses will appear on floor 33.

Act 3[edit | edit source]

One of these bosses will appear on floor 50.

Act 4[edit | edit source]

Corrupt Heart appears on floor 55.

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