Combos Utilizing Witch-Engine

sacrifice the witch engine using sadistic hypnotist and then use its ability, so you can use the mana and not loose the witch engine to the other player

play witch engine and overtaker, when you tap and use witch engine for mana, take it back with overtaker.

the witch engine gives u 4 black mana cool, use the engine then give your opponent the engine then play plauge wind so he/she never gets to use the engine against u and u destroy all there creatures

turn all lands into swamps and attack with an unblockable creature

Have pestilence in play, then use the Witch Engine tap it to add the 4 black mana to your mana pool, then use it to hit them for 4 and kill the witch engine so they cant use it on youl

if u need mana, use all of these +1 more dark ritual and u'll get 16 swamps to use

turn opponent's land into a swamp & Witch Engine is unblockable