Wandil is the first boss you encounter in Snowcloak. Of the three bosses, this one requires the least mechanical awareness. Really all you need to do is watch out for Cold Wave and kill bombs.
Yeti is actually a pretty fun fight. It's not your usual hold it in one spot boss and burn it down. This fight is all about positioning and patience. Yeti only actually has three attacks, but if the mechanics aren't done right this fight can drag on. Yeti seems to either take reduced damage or have an enormous amount of HP.
Frozen Mist: A Conal AoE attack that damages all players hit and traps all Spriggan Icecutters in Snowballs. Hitting a Snowball with Frozen Mist makes it larger, this caps at the third size.
Buffet: A wide conal AoE attack in front of Yeti.
Northerlies: A room wide AoE that can be interupted by hitting a Snowball into Yeti. Interrupting this attack with a Snowball does considerable damage. I'm unsure if the size of the Snowball has any effect on how much damage Yeti takes from it.
Adds: There are two types of adds that spawn: Spriggan Icecutters and Frostbound. Frostbound should be burned down when they spawn. Spriggan should be huddled up if possible to prepare for Frozen Mist.
An iconic Final Fantasy figure, Fenrir has been both a boss and a summon in the past. In this fight you get to see some interesting new spins on old mechanics with something that's all new. For a bit of a laugh, you get to see what happens when you take a pillar to the face. Our Dragoon got hit in the first rotation.
Heavansward Howl: A frontal cleave breath attack dealing moderate damage.
Thousand-Year Storm: A room wide attack that deals moderate damage to all players. This attack can't be stunned or silenced.
Ice Shard mechanic: Fenrir telegraphs this attack with a fancy animation prior to the ground markers appearing. Three pillars will drop from the sky randomly. Upon landing two of these pillars will target players and shoot themselves at them. The other pillar will remain where it landing, exploding after a set amount of time. The third pillar will be used during Lunar Cry.
Lunar Cry: A room wide AoE that instantly kills anyone it hits. After every second set of pillar drops Fenrir will instantly start casting, so move to the remaining pillar and line of sight Fenrir using the pillar. After Lunar Cry is cast players need to leave the pillar before it explodes.
Ecliptic Bite: After Lunar Cry Fenrir jumps to the tank with Ecliptic Bite dealing moderate damage.