Tetra is a Valheim creature typically found in the mountain biome from the Fish faction. Its character ID is Fish4_cave, and the cheat command spawn Fish4_cave summons one in front of you — append 1 2 or 1 3 for one- or two-star variants. Spending its whole life in the dark, it has no need for eyes.
Tetra are docile fish discovered in the exceptionally rare lakes situated at the base of Frost caves in the Mountain biome.
To reel them in, a fishing pole equipped with Cold fishing bait is needed. This bait can be concocted at the cauldron by blending 20 Fishing bait with a Fenring trophy.
Spawns one Tetra at level 1 (normal).
Spawns one Tetra at your location.
Spawns one Tetra at level 2 (use 1, 2, or 3).
Spawns five Tetra at your location.