Amber Seals (also called Bubbles) are massive, egg-like containers woven by The Sentinel and used as incubation chambers for growing monsters. These organic structures are found deep within underground warrens.

An Amber Seal is completely indestructible from the outside; only a creature born within can break through it, and only when its growth is complete. Some creatures that undergo long hibernation instinctively return to their original warrens—many can even re-enter their old Amber Seal, sealing themselves inside until their hibernation ends.