The ones created by TU reset after two attacks. So say you have a 5 attack wyrm, dive it to 10 attack, then TU it. It attacks with 10 attack and stays. The next turn, you use dive to get 20 attack, then it attacks again and returns to 5 attack. But if you TU it between diving and ending your turn, you get a new wyrm with 20 attack that won't reset until the next turn. This way, if you use a TU every turn, you can keep doubling the attack. I used blessings, chaos powers, and rage elixirs on the original wyrm to speed things up a bit.