In (LCPT), was introduced in version 0.2.999 as part of a specialized Halloween-themed update. To unlock this character, you must engage with the Halloween Dark Ritual mechanics and specific cosmetic items . Mal0 Unlock Guide
For similar characters like the Jack-o'-Lantern Girl, players must equip the Pumpkin hat on a character within the Ritual background and complete a full piston cycle until the "climax" is reached to trigger the unlock. how to unlock mal0 in lovely craft piston trap
Here is the breakdown of the mechanic and the narrative weight of the unlock. In (LCPT), was introduced in version 0