In the room containing the Lifeblood Core charm, a massive, multi-eyed head can be seen opening its eyes in the foggy background, moving up and down slightly as if breathing. It makes no noise, and cannot be interacted with in any way. It is referred to in the game files as "Abyss Creature", though only the head sprite exists for it. Any specific relations to Lifeblood or the rest of the events in Hallownest are, as of yet, unknown.
The Abyss Creature can be seen again in a room behind the blue door in Godhome. The meaning behind this appearance is again currently unknown but furthers the connection between this being and Lifeblood as well as point to it possibly being some being of greater power.