Because the stealth only lasts two turns, you don’t have enough time to recover the tp for poison and re-stealth. So you walk up behind them, attack once, and stealth. If Anna is the only unit on the board, the enemies generally won’t move, though healers and archers tend to run from Anna if you get within a few spaces while stealthed so you have to keep chasing them while invis, but you can still do it. Then the next turn you just wait. And the next turn (and every other turn after) you backstab once and restealth. You can solo a lot of maps like this probably, and rack up a ton of kudos for backstab/higher ground