The E 25 (also nicknamed by some of us as the Devil or COCKroach, although the latter is reserved for the T-54) is a tier 7 absolutely balanced tank destroyer that only sees tier 5-8 tanks. It's got a 75 mm that shoots ungodly fast (with a good crew you get about 3 sec reload) which has crappy standard ammo pen but good-ish gold pen.
In real life, the E 25 (E stands for Entwicklung = Development) was one of the tanks that were part of the Standardpanzerprogramm. The E 25 was designed as a light tank destroyer made especially for reconnaissance (much like its smaller cousin, the E 10). It would've likely replaced the JgPz IV and the Hetzer.
*Uniscrub guide to the Cockroach*
Pitch and Roll make it move faster than light.
VTOL+Trim are used to move its filthy head around. (aka the gun / AG8)
AG1 activates the spare head. It also comes with a peashooter against enemy bugs (use VTOL+Trim for it).
AG3 for when you're too dark so you gotta light yourself up. (activates the lights)