Mol-Qayin is a large, blob-like boss similar to Sludge Heart but with different attack and defeat strategies. Mol-Qayin appears to be a smiling ball of glowing magma with a purple crystal column that sticks out of its forehead.
Mol-Qayin will do nothing but smirk smugly at The Player until provoked. Mol-Qayin will move by jumping up and away from The Player's current location and attack by spitting out a group of dangerously-hot magma orbs. Mol-Qayin will jump away again and perform its only other attack; it takes a deep breath and spits out a large black sphere that embeds into the floor. When this sphere contacts magma, it explodes, so be wary to avoid it, but note that this hints at Mol-Qayin's defeat strategy. Mol-Qayin will continously spit magma at The Player, becoming smaller each time, but the magma will pull itself back into Mol-Qayin after landing.
To beat Mol-Qayin, shoot it in the mouth any time that it has it open. Miraculously enough, the arrow will not burn but it does become trapped within Mol-Qayin's body. Any attempts to summon the arrow will pull Mol-Qayin along with it. The trick is to pull Mol-Qayin into its own explosive sphere, which will send pieces of the titan everywhere. The arrow can now be retrieved, and to defeat Mol-Qayin it must be shot back quickly at the crystal pillar left behind before the titan reforms itself. Damaging this column will destroy Mol-Qayin.
- The first part of the name Mol-Qayin, Mol, is taken from the word molten.