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so, to make it both fun and original, we need to create a huge underground worm, like in Dune^^
like, a worm-a scary worm-an evil worm:)
I've even come up with some details:
the worm's ability is to devour a unit;) - it eats the entire stack, if "Major, add a formula here, most likely based on the worm's HP and the attacking stack's stats xD", then the stack is completely devoured, gg to him:) if it's too strong, then let the worm lie down for a couple of turns, digest, and not move:)
if the Major's formula gives a result that is not in favor of the worm, then it will lie down for a couple of turns, digesting, and then spit out the half-digested stack, without causing any harm to it, but disabling it for those couple of turns:)
a scary worm - it can burrow in the ground and move across the entire map in one turn, like the Devil from Might and Magic IV, that's why it's scary))
an angry, unfed worm - it's so angry and hungry that it can devour two stacks at once, standing on adjacent cells=)
and a little more:
the troll with armor inspired a creative idea - a siege worm-killer)))
covered in spikes, with an artificial iron jaw, like the Warbosses:)))), it can devour a castle tower)) and in general, it is stronger and more resilient than the others (because castles are captured much less often than simple battles in the open field).
a worm that ate something bad for breakfast - when "walking", it leaves a stinky trail behind it, which acts like a moat (stopping a unit and damaging it):P, maybe it can spit this at enemies or in an empty space, creating "moats"))) it looks sad:(
a happy worm - it is happy because it spends its whole life dividing%)
after devouring a squad, with a probability of "Major, it's your turn:))", it adds one more to its squad. if it's too strong, then once per battle, and let the chance be small)) it looks happy)
an exhausted worm - it feels bad after yesterday, so once per battle it can let the enemies know how much its head hurts(?), by throwing something terribly mental at them, for example, damaging and possibly paralyzing them.
a worm-dad (or worm-mom, or captain of worms)))))) - it really likes to spew out small, tiny, gluttonous, slimy, stinky, wriggling worms when it attacks, which will reduce the enemy's armor and lower their morale, because who likes it when some kind of... mmm... substance sticks to their body?
all worms know how and love to eat, and a hungry one does it up to two times in one go%)
here are my creative ideas, bordering on madness xD