Megatons spawn two rounds after the Pack-a-punch has been built or on Wave 13 if the power has not been restored in Die Maschine, while they spawn randomly across the map in Outbreak.

What rounds do the megatons spawn?

A Megaton is a large, muscular zombie that wears a torn hazmat suit that sports patches that of Omega Group. It emits a green glow all around, with a stronger glow from it's eyes and hands. They spawn two rounds after the power has been turned on. If the power is not turned on, they will spawn on round 15.

Do megatons stop spawning?

Megatons seem to dissapear/respawn when entering or leaving the Dark Aether. This is likely unintentional on the developer's part, but players should utilize this oversight to get some distance between them & a Megaton if their damage isn't quite high enough yet.