From 2speccers2tools wiki

The Nostalgia feels familiar somehow…hmmm…but regardless of this, it evolved from the rogue citadels and has developed a bilateral shape and gastropod-like locomotion, it moves along slurping up biofilms (including its former creators ironically) and detritus on forest floors like a strange roomba, it is significantly smaller than its ancestor as its diet cannot sustain its previous size any longer.