The 吮腦怪 is a 困難模式, post-拜月教邪教徒 flying 敵怪 spawned by the 星雲柱 during the 月亮事件. It latches onto the player's head, dealing large amounts of damage at a steady rate, while also inflicting the 阻塞 debuff for the remainder of it time it is on the player.
- If the player teleports using a 魔鏡, 冰雪鏡, or a Cellphone while a Brain Suckler is still attached to them, the Brain Suckler will teleport with the player to the player's teleport-ed destination.
- Brain Sucklers pay homage to the iconic Headcrab enemy from the Half-Life series, as they attack by latching onto a player's head and disrupting their brain functions. Brain Sucklers are referred to as Nebula Headcrabs sporadically in the game's code, and in their banner prior to a patch, implying their name was changed at some point during development.
- They are also similar in appearance and function to the Metroids from the series of the same name, in that they latch onto preys' heads and drain their life force.
- ??：Name changed from "Nebula Headcrab" to "Brain Suckler".
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