"A special slime with thorns protruding from its body. They're small so use a downward thrust."
Zelda II: The Adventure of Link manual

Myus are enemies from Zelda II: The Adventure of Link. They inhabit caves and some palaces and inch along the ground in a fashion similar to Bots. They are also protected by several white thorns that extend out of their body. Myus are so small that Link cannot hit them with a standard sword thrust, even while ducking. The easiest, and often only, way to hit them is with the Downthrust.

When found in palaces, Myus are often on disintegrating bridges. Link must jump to avoid the Myu and to avoid being dumped into the water or lava under the bridge. There is a particular kind of Myu that lives in the Great Palace. Although visually identical to other Myus, this one is much more powerful, as it deals more damage to Link and requires more hits to kill. Interestingly, if Link keeps a certain distance from them after killing them, they can regenerate.