To tame a otter, you have to kill a Fish, the Best one is salmon, drag the Fish to otter, and feed it. Repertuar that until it's tamed. If you have problems to tame it, kill bigger fishes, I prefer 1.5x and higher.

After you have tamed it, feed it raw Fish meat, and pick it up. Otter gives you higher hypothermic, and hiperthermic Isulation. It can have multiple artifacts, that ark the same. For example, you can have 3 artifacts of the hunter, in otter's inventory. Otter has very low hp, so pu point in his Heath stat, and give him helmet.

Sorry for bad English

-KubaPL