In Mystery Of Wistimere, the four horses carried the Vermin to Wistimere, protected by Vesper, Lola Windwisper, Auberon, and Valori in a deadly Troll encounter. Their carriage would prove useful in shielding Luana Yinshera from the prying eyes of the public and Mayor Perceval LaPall as the adventurers solved the mystery plaguing the town.
A Riding Horse native to Oldoan, Oreo was raised in stables belonging to Vermhaxaandes Sharhydrox. High-energy, happy, and "talkative" for a horse, she was considered by Hydrox to be one of the few horses of his retinue reliable enough for Adventurers.
Oreo eventually became an animal companion of the Vermin alongside cousins Ginger, Fudgeeo, and Biscuit, and she became the usual steed of Vesper.