When that creature becomes blocked this turn, it gets +1/+1 until end of turn for each creature blocking it
The cards other ability is Protective Embrace, which grants other characters on the players battlefield the Ward status thereby forcing the opponent to either target other cards with attacks or overcome a Challenge to attack warded cards
Aether Revolt 4 mana is a bridge too far for Modern, but Aether Revolt gives teeth to energy combos in Commander, which right now struggle to win the game
Land Color tag templates(None) Crumbling Necropolis This land enters tapped
If the target creature is an illegal target as Hydaelyn, the Mothercrystal's last ability tries to resolve, it won't resolve and none of its effects will happen
Combined with Food, Clues, Treasures, or even just general artifact recursion lists, this both gets huge and lets you see a big chunk of your deck rapidly