From Creatures Wikia
The Yeren Grendels are a breed of Grendel that come packaged with Ostrova, a metaroom created by Chaos Development. They are said to be a yeti hybrid, which is the origin of their name--Yeren being another word for yeti. Although they are rather cute, they are still Grendels, and can be deadly when encountered by norns. Their albinism allows them to blend in with Ostrova's icy regions, but can also lead to many interesting color variations.
The Yeren Grendels use Grendel slot I.