An earth pony Sombra Soldier as a member of the Iron Grenadiers, Destro's elite troops, from G.I. Joe.

The design of the Sombra Soldier helmets had always kind of reminded me a bit of the Iron Grenadiers helmets (another reason I chose Sombra for Destro in this fusion series). As the Iron Grenadiers are meant to be mercenaries rather than slaves, however, I figure in this instance the helmets wouldn't mind control the wearers. Instead, I imagine the effect would more likely be performance enhancement and emotional dis-inhibition, making whoever wears them physically stronger and more aggressive.