If Fecund Greenshell's second ability stops applying (because Fecund Greenshell leaves the battlefield or loses its abilities or because you no longer control ten or more lands), then any creatures that needed the toughness bonus to stay alive will die
For example, if Sandman is blocked by a creature with 4 power, and then an effect gives that creature -3/-0, it won't stop blocking Sandman
Protection spells, like Crypsis and Take Up the Shield, are also great with Zethi since you have to attack with them to trigger their ability
(To mill a card, put the top card of your library into your graveyard.) Though imprisoned in Jaspera trees, the elvish gods known as the Einir still whisper through the ages
Its fun, it causes interesting interactions, and some effects even play well with the increased use of negative counters like finality and stun counters
Marath, Will of the Wild Arguably the best commander in Tiny Leaders, Marath, Will of the Wild grows every time you cast it thanks to commander tax, turning +1/+1 counters into real power over the course of a game