Here are some ideas for some new enemies! Some of them will be more ambitious and others, and I will probably say if an enemy is too ambitious or not. I would recommend people adding to the discussion with their own ideas!

Swine rider
Names: Swine rider for apprentice, swine cavalier for veteran, swine wormlord for champion

Worm Steed
Names: Worm steed for apprentice, worm mount for veteran, worm siege weapon for champion

The swine rider and worm steed is a midboss enemy, similar to the Crimson Headsman. When together, the ridden worm steed as its called ingame. It has two turns when the swine rider is riding the worm. They have two attacks when the worm is being ridden, the rider fires from a crossbow and the worm could attack. The worm attack while being ridden will mark a hero, and the crossbow attack deals more damage, but its target is always randomized(the rider is riding an unwieldy mount, thats why). At half health, the rider will dismount. The worm will use a very inaccurate, but damaging attack. The rider will either shoot his crossbow(No random targeting this time), or patch up his steed. The worm, if its at more than half health from the riders healing, will let the rider get back on it. Keep in mind that due to them being separate, their turns are now separate. This creature might actually be really difficult to code, however, mainly due to the dismount and remount thing, but remounting could maybe not be a part of it so that its easier to code.