In Mortal Kombat: Defenders of the Realm, Kiba acts as Nightwolf's spirit wolf, although he also doubles as a friendly and playful pet. While his loyalties are bound to Nightwolf, he keeps friendly company to any and all are left to guard the Cave alone while the rest of Earthrealm's defenders are out fighting.
Kiba's most prominent role is acting as Nightwolf's source of power, turning him into an avatar and giving him his powers and face marking. Kiba initially had an uneasy relationship with Stryker, but later became his friend.
A spiritual wolf appears in Nightwolf's MK 2011 ending, but it is not confirmed that it is Kiba. But the spiritual wolf is likely the inspiration for Kiba.