A key to open the main gate at the Asylum and all the doors in it and throughout the rest of the game. It looks like a key stuck in a glove. It is located in the Asylum: Gateway after battling past all the slaughter rooms filled with Hookmen. The Engineer's Key receptacles are usually located near a locked door, equip the key and use the action button to open the door. When the blue light on the receptacle is lit up you'll never have to use the key again. If the light flickers and fades out then you can use it as many times as you need to for moving a platform from left to right etc. Shadowman will also need the Engineers Key to progress through the game to activate the Train in the Asylum Cageways.