Kingdom Rush Origins (Steam) Impossible Hero Challenge - Grimmsburg Iron

So this map is very analogous to Grimmsburg campaign - it's trivial aside from the Gloomies.  And as with that map, the key is to put together a plan that takes care of them without relying on your hero.  And while the micro here is tricky and you do need to know exactly where to put reinforcements and when to use Venom Vines, ultimately it's not as challenging as the campaign mode.  I considered doing the same thing here as I did for that map - giving every hero whose Hero Spell doesn't help with the Gloomies a B - but once I had the micro down I didn't have nearly as many slip-ups as with that map, so we're just going to give everyone an A.

Kingdom Rush Origins Impossible Hero Challenge - Grimmsburg Iron