Frost Minnow

The Warmth Potion is the reason to hold onto these. Cold damage is a small tax most of the time, but the ice caves, Deerclops and the Frost Moon all pile cold sources on you at once, and a stack of the potion turns a miserable stretch of a run into an ordinary one. The Seafood Dinner is the lesser payoff, though it is a cheap way to fill the well fed slot before a boss.

They only bite in water inside the snow biome, and they are not a common pull, so plan on a long session rather than five casts on your way past. Any depth counts, which means an underground pool works and is a lot safer than sitting on the surface after dark.