Sonju's horse

Sonju's horse is the unofficial designation of a demon horse ridden by Sonju in The Promised Neverland.

Promised Forest Arc
Before a group of demons could capture Ray, Sonju and his horse save Ray in the nick of time.

Search For Minerva Arc
Somewhere in the forest, Sonju and Mujika were about to ride the horse, Mujika stared towards a distance and smiled. Sonju asked her what is up, to which Mujika replied how she was fine as she proceeded to ride the horse with Sonju.

Trivia

 * Sonju's horse bears a heavy resemblence to the Sleipnir, the noble steed of Odin in Norse Mythology.