How Do We Survive This?

[Oofta]

If Fog Cloud is not an option, closing your eyes/not meeting their gaze would help with the Chilling Gaze. The downside is that you will have disadvantage to hit and they will have advantage to hit. Their AC isn't too high, and their damage output isn't amazing, so you could still out damage them probably.

Knowing the spell layout of your group would be helpful to provide other ideas ( if it was in an earlier post I missed it ).

The druid is supposedly a straight NPC from the book. So druidcraft, produce flame, shillelagh, entangle, longstrider, speak with animals, thunderwave, animal messenger, barkskin. The arcane trickster is only going to have a couple of wizard illusion/enchantment spells. Although they might have disguise self so maybe he could disguise himself as a female yeti and hope for the best? Have the druid cast longstrider on him and distract the ambushers?

 

[Lucas Blackstone]

Color Spray (1st level illusion) blinds a creature if the hit points are lower then the rolled 6d10. A wounded yeti ( I wouldn't count on rolling the 51 hp needed to blind a full health one ) that is blinded can't trigger it's chill gaze, and also provides all the other benefits a blinded enemy does.Also the Arcane Trickster should have access to one non illusion/enchantment spell. What that spell is could make a difference. Knowing what tools are at hand helps is all. The aforementioned Fog Cloud is a legitimate selection for the arcane trickster non-illusion/enchantment spell known and would make this a much easier fight.

Longstrider on the rogue + ranged weapon also is pretty valid in providing sustained damage without danger. It doesn't save the others, but even if they all became paralyzed I don't think the yetis would sit there and eat them while being shot over and over.

Question/comment involving Fog Cloud and sneak attack. I saw mention of sneak attack not working because of not being able to see the enemy. Since the enemy couldn't see the rogue either, the rogue does not have advantage or disadvantage. So couldn't the rogue sneak attack as long as an enemy of the target is within 5 feet of it? At least I thought that is how it worked.

 

[Dausuul]

If the Druid can get a well placed spike growth off you can kite them and hopefully cause enough harm that they break it off and don’t pursue and fight to the death

The druid doesn't have spike growth. Doesn't have Wild Shape, either. It's a Monster Manual "druid," not an actual druid PC.

Question/comment involving Fog Cloud and sneak attack. I saw mention of sneak attack not working because of not being able to see the enemy. Since the enemy couldn't see the rogue either, the rogue does not have advantage or disadvantage.

Edit: You are correct. I thought the rogue had both advantage and disadvantage, but then I re-read the rules: If you have both, you are considered to have neither.