For the final battle:
Once you destroy the enemy tower the main boss comes. Be prepared. Have 9999 mana, a barrier, a turret, a trap, and your hobbits, angels, and all arrows maxed out.
Spam angels and hobbits. The angels will destroy the troops coming from behind him, while the hobbits will make him have to fire while the angels are not around. When he fires he's stopped and therefore not moving closer. Fire from the most downward angle you can. The special arrows seem to continue to hurt him all the way through him and downward gives the longest distance to travel.
I beat it without him even making it past the last mountain towards me.
Have fun.
BUG: 4 geothermals with 1 level of upgrade say they produce 15 each. But on the power grid i actually begin gaining less per tick (with no other changers) after the upgrade. (When hovering over it says they're only outputting 30 and i have a drain of sixish for a gain of 24 per tick.)
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