Bio-mechanical supercomputers built by the enigmatic Ancients of Rain World. Their "bodies" consist of a massive supercomputer and an android-like "puppet" which acts as an interface. Any damage done to the computer appears to be felt and expressed by the puppet.

Their purpose was to ponder on the breaking of the cycle of death and rebirth that all beings on the titular world endure. This was rendered moot with the eventual discovery of "void fluid," a highly volatile liquid that dissolves and permanently releases living organisms from the shackles of mortality, turning them into ghostly ethereal beings that linger as Echoes in the physical world for eternity if they do not let go of earthly desires.

After the mass suicide of their creators via void fluid, and being unable to do so themselves, their duties were twofold: to ponder for countless years on an alternate means of "ascension," and to spread the wisdom and enlightenment of their people to lesser beings (like the Slugcat) so they, too, could fling themselves into the void fluid.