Repurposed oversized video game controller the Sledge still clutches, his link to the missile system.
The Sledge sits staring sadly off into nothing, still clutching the repurposed, large-sized video game controller for the missile system, with Princess Donut perched on his shoulder.
The controller is the physical half of a capability nobody else can take up: Edgar can't tattoo a rock or extract anything from him, and a Changeling is unlikely to lift a spell that Cretins don't normally have. Rosetta concludes that they'll have to manage — meaning the Sledge and his controller remain the only way to work the missiles.
An oversized video game controller, scaled for enormous stone hands and rewired to drive a missile system.
Interface linking the Sledge to the missile system, and unique to him.