PokéIsaac bosses guide

How boss fights work

• One boss per floor. Each floor picks its boss from that area’s pool, so you will not see the same boss every run.
• Two phases. Floor bosses switch to a harder attack set at 50% health, often summoning their pre-evolutions.
• Telegraphed attacks. Lines mark charges and beams, filling circles mark falling attacks, cones mark flamethrowers, rings with a gap show the way out, and columns or half-room zones mark big area attacks. Red means a hit is coming now, yellow marks a cone or gap, and violet marks a zone that stays on the ground.
• Rewards. A boss item and a trapdoor to the next floor. Sometimes a rift to Darkrai or Jirachi opens too; a fight where the boss never hits you makes that much more likely.

Floor 1: Viridian Forest

Most bosses here are Bug type: Fire, Rock and Flying shots all deal ×1.5.

Floor 2: Mt. Moon

Rock bosses with one Steel exception. Water (or Ground and Fighting) handles all of them.

Beating the Mt. Moon boss unlocks Squirtle.

Floor 3: Pokémon Tower

Ghost bosses that teleport and clone themselves. Bring Ghost or Dark; against Marowak switch to Water or Grass.

Beating the Pokémon Tower boss unlocks Bulbasaur.

Floor 4: Cinnabar Mansion

A mixed pool. Ground is the safest single answer: it hits Fire, Poison and Electric bosses super effectively.

Floor 5: Mewtwo

Mewtwo (Psychic, 720 base HP, signature Psycho Boost) guards Cerulean Cave. It teleports, fires homing shots and sends waves with a gap you have to slip through; in phase 2 it adds a barrier and a laser. Ghost, Bug and Dark deal ×1.5. Beating it unlocks Eevee.

Deep floors (6–29)

From floor 6 any floor boss above can appear, plus five new ones. Mewtwo or Mew guards floors 15 and 25.

Base HP is multiplied as you go deeper: ×2.5 by floor 10, ×6 by floor 20 and ×12 by floor 30.

Floor 30: Armored Mewtwo

The Classic mode finale. Armored Mewtwo (Psychic, 1,650 base HP, signature Twin Cannon) wears five armour pieces you can break, and each one you destroy takes something away:

Pieces crack before they break. At 60% health the remaining armour flies off, at 30% it breaks free, and at 15% it Mega Evolves into Mega Mewtwo Y for a final phase with Future Sight. Like every Mewtwo, it is weak to Ghost, Bug and Dark.

Tips: break the breastplate first to stop the damage reduction, then the tubes to get rid of the homing Psi Missiles. Save an invulnerability active item (Max Repel, Energy Root) for the final phase.

Beating it ends Classic mode with a cutscene, earns a profile trophy and opens the Mega banner in the Gacha. You then choose to end the run with the win or continue into endless mode.

Mega bosses (every 10 floors)

On floors 10, 20 and every 10th floor after, the run picks a shiny Mega boss (no repeats within a run). It starts in normal form, Mega Evolves at 70% and enters a final phase at 35%. Beating one gives double rewards: two rounds of items, eight item unlocks instead of four, and 2 Mega Tickets (Armored Mewtwo gives 5; in endless mode the floor 40 Mega boss gives 10, floor 50 gives 15, and so on).

The pool includes 37 Megas such as Mega Charizard X, Mega Gengar, Mega Lucario, Mega Gardevoir, Mega Banette and Mega Eelektross. Fixed milestones in endless mode:

• Floor 50: Mega Rayquaza
• Floor 80: Mega Latias and Mega Latios together
• Floor 100: Mega Mewtwo Y

Mega bosses also roll affixes: one on floor 40, two on floor 60, three on floor 90, and one more every 50 floors from floor 100. The possible affixes are Armored (a shield to break first), Swift (faster attacks), Summoner (calls minions each phase), Mirror (reflects one shot in ten), Vampire (heals when it hits you) or Furious (starts in phase 2).

Darkrai

In the violet Distortion Room, Darkrai usually sells deals. Once per run there is a 10% chance it attacks instead: a Dark-type fight (240 base HP, scaling with the floor, weak to Bug, Fighting and Fairy) that drops a Charcoal. See Darkrai deals.