My strat for 3 staring in case people are interested :Use lightning rods (in the form of princeses/fencers/valks) right at the entry on the top left , to make the drake attack said side , were u will have no units placed. Try to drop the drake near claudia , and then retire everything outside of the 2 healers (and ofc claudia) , and activate her skill. The drake will die before the skill durations ends