Ulv has 50 health and spawns in the mountains.
It takes extra damage from poison; it resists fire. Blunt, slash and pierce land at full damage, so that is what to bring.
Its hardest hit is 1 bite at 80 slash, out of 2 attacks.
Of everything craftable, 
Frostfire Crossbow, 
Thunderblood Crossbow and 
Lightning Strike put the most damage through what it resists.
Ulv is a four-legged wolf creature that spawns in packs of up to nine inside Mountain Frost Caves and Hildir's cave. It has 50 health and a run speed of 8, is very resistant to fire and weak to poison, so torches and fire arrows are close to useless against it. It bites upward for 80 slash every 5 seconds and rears back for a 70 slash downward swipe every 9 seconds. It drops 1 to 2 
Wolf Fang half the time and an 
Ulv Trophy at 10%.
Nearly fireproof but weak to poison, which makes them one of the few good targets for a poison-coated blade. Their lunges parry cleanly, and the narrow cave halls funnel them into your shield one at a time if you back up.
With devcommands enabled, this spawns Ulv in front of you. The third number is the level: 3 spawns a 2-star.
Creature ID: Ulv · all console commands and IDs