Since myth has the most minions, and the most aggressive minions. I thought they could have a spell that copies one of the monsters you were fighting, and makes it into a minion. It would be a high level spell You wouldn't be able to copy boss type monsters. I would like it to fight using the monster's own deck, and AI. I guess it could have less health...
This may conflict with the renting of henchmen... On the other hand the doppelganger minion would be the same type as the monster you were fighting... There are plenty of stories about doppelgangers, I figured it could fit myth's flavor.
Sounds like you've been watching sci-fi movies(!) all of THAT sounds like a sheer possibility!!!!-worthy of, at least something popular... I think a lot of OTHER stuff in addition to that could fit too! If you have ever seen the movie "Independence day", you'd see that you could add alien-like (not like little green men) creatures armed with something like a pike with a electric blade at both ends, a metal sword that is glowing with and humming with the sound of electricity, a machine gun that rapidly shoots tiny balls of energetic matter, or a whip made of energy added too the game (keep in mind-there is minimal reference to it in both wizard 101, and the movie Independence day). Mostly, the "monster copy" spell should be a new feature too!
P.S if only that was already a game feature- for the gaming record, you just spat out a phonemically interesting game idea, you could also get the other good stuff with it- but ONLY if the powers that be will allow it- you TOTALLY deserve support for that idea. good luck!