Pure Titans

The mindless Titans that Eldians injected with serum turn into: they roam and devour humans with no need for food. For a century Marley created them by exiling "traitors" to Paradis.

Abnormal Titans (奇行種) move unpredictably. A pure Titan only turns human again by devouring a shifter: that is how Ymir obtains the Jaw and Eren, as a child, inherits the Attack and the Founder from his father. The Titan that devours Carla is Dina Fritz.