Incomplete One

Incomplete One is the first keeper in Dead Cells. It's found on the Black Bridge.

Attacks
Incomplete One constantly walks towards its aggressor. It starts with one attack:
 * When within range, it will reel backwards and thrust its claw forward, doing ~65-100 damage.

At 90% health, it gains two more abilities:
 * It roars, causing a soundwave which stuns the player if they are within range. Using this ability gives the Incomplete One a force field, making it immune to all damage until it dissipates.
 * It summons a red aura around itself, which does 21 damage per tick to anything within it.

At ~80% health, it gains the following ability:
 * It sweeps its claw upwards, creating a wave of fire that moves outwards in both directions, doing ~35-50 damage. The flames can't be rolled through.

At ~65% health, it gains the following ability:
 * It jumps toward the player, doing ~55-71 damage.

Tips
Range is your friend with this fight. If at all possible, grab an Electric Whip and do your best to keep him at max range. When you get backed into a corner, dodge roll past him when the red aura is down, to the opposite side of the arena.

Keep in mind, because of the way ammo works in this game you cannot use most ranged weapons by themselves, as the ammunition will get stuck in the boss and will not regenerate. The Electric Whip, Bow and Infinite Arrows and Lightning Bolt are some ranged weapons where ammo is not an issue. Other helpful weapons with range include the Impaler, the War Spear, and nearly any of the available Skills. Using the Magnetic Grenade is also recommended, as it will pull the Incomplete One over to it or slow it down if it continues to approach you. This can be used to deal continuous damage, trap it in one area for certain attacks, and buy extra time for you to heal.

Not sure but I think that ammo does return to you after a few seconds. I used Infantry Bow, but I don't know was it bug or just bows can be used against this keeper. (edit; the ammo can return when emeny is frozen and broken out of the freeze as i have found in my runs against him)

Not sure if this is a bug or not, but the Ice Bow will regenerate ammo even if the boss is not dead. This gives you a quick and easy way of freezing the boss to reposition, heal, or wait for cooldowns. (My ice bow did regenerate one time and the next time it did not)

Stuns and freezes work on this boss. Use this to your advantage to reposition to a more favorable location.

Watch out for his jump -> thrust combo. this can do ~150 damage very quickly. Try and dodge his jump by rolling underneath him, he will generally overshoot and be out of range of his thrust.

Healing can be difficult during this fight. Due to the boss's ability to quickly move around the map, as well as cover the entire floor in fire, make sure you have the attack patterns down before you try and heal. If you're a little low, try and heal up before you get him down to 65% health, so he cannot jump on you.

Phaser can be used to get behind the boss's highest damage attacks, and provide you a fairly safe way of getting around him if you mess up a dodge. consider grabbing this if you do not have a ranged weapon you can use for this fight. Keep in mind to not Phaser if the boss is using his AoE.

There are several ways to disrupt the Incomplete One's attacks. Ice Grenade and Frost Blast can freeze the boss while his shield is up, and the Meat Grinder will cause bleeding through his shield. If the boss walks through fire while the shield is active, he will suffer burning. There are also a number of ways to stop the Incomplete One from activating his AoE attack. While he is charging up the AoE, if you knock him off of the ground with a Grenade or stun him with a Flashbang, he will not trigger the AoE. You can delay the activation of the AoE by freezing him, but he will continue after unfreezing.