From Brotato Wiki
Elites
Elites are special enemies that only appear on certain waves. If any elites will spawn in a run the the player will be notified in the [1]. No elites will spawn in dangers 0, 1 or 2 but 1 wave can have an elite enemy on [2] 2 and 3 and a maximum of 3 waves can have a elite on it on [3] 4 and 5. If you kill an elite then it will drop a red crate with a guaranteed drop of a legendary item in side of it.
Mutation 0
(initial phase) Charges to the player every 2 seconds, shooting projectiles to its left and right during the charge.
Mutation 1
(60% hp or 25s left) Charges to the player every 1.3 seconds for shorter distance, shooting projectiles to its left and right during the charge, at the start of its charge fires extra 2 projectiles.