the most busted things in this are kartana, magearna, regenerator/volt absorb/water absorb, and defiant/competitive as far as i can see, all of those are absolutely obscene. mummy is fun tech to shut off some of the more broken shit. static/effect spore/poison point/flame body are all really nuts too if they work the way i'm assuming they do
how does battle bond work with this? unburden? does hydration trigger outside of rain? do abilities go off according to speed order? how does this interact with abilities like speed boost and poison heal that already activate at end of turn? where do these effects fit into the end of turn resolution order?
Honestly i think the absolute worst ability is Truant, because if it ONLY activates at the end of each turn, it means slaking does not become a burden, he can still attack every turn