I would love to see Magikarp flopping around the map as a Demigod, and his only skill would be "Evolve" which would turn him into Gyrados and do instant-kill hits. But activation would take two seconds and he would only be evolved for five seconds, and the skill would have a 45-second cooldown.
That way you'd have this fish flopping into a massive melee and hitting activation, and all enemy demigods would be like "OH NOES IT'S THE FISH-DRAGON RUN!" and they'd run like hell for as long as he stays evolved lol.
... Although maybe he should have another skill called "Splash" which would have him splashing into the ground (mysteriously) and doing 200 aoe damage to units in immediate melee range. This skill would have a cooldown of three seconds.
Maybe I should make a "New Demigod Idea" thread.