So this looks wonky. I wanted to do a reserve creature with flash. I wanted that creature to be a mid-sized aggressive creature with maybe some evasion. Deathtouch seemed the best route for evasion in mono-green. I didn't want Ambush Viper though, so I added the clause to make deathtouch only when attacking. Essentially, I want the creature cast after combat on the opponent's turn, so that the creature can attack on its controller's turn.