The creeper is a strain of primal zerg spawned by higher strains.
Heart of the Swarm
Creepers appear in Heart of the Swarm, where they are spawned by Slivan. They detonate a few seconds after reaching their target in a manner similar to banelings, but move slowly, hence allowing Kerrigan time to move out of the way even as they begin to detonate.
Creepers are spawned by creeper hosts in Co-op Missions. Like locusts, they fly, and swoop down to their targets, but unlike locusts, they detonate on impact. They deal bonus damage to structures. Murvar can spawns explosive creepers if Dehaka reach level 10 in talent progression.
Upgrades and Abilities
Flying Volatile Creeper
Allows volatile creepers spawned by creeper hosts to fly. Flying volatile creepers can use swoop to land and attack.