edhseer Commander synergy, explained
Land
If you control two or more other lands, this land enters tapped.
static —
Add {U}.
activated {T} — adds 1 mana
Until end of turn, this land becomes a 7/7 blue Giant creature with ward {3}. It's still a land.
activated {5}{U} — turns something into a creature
Causes: nothing.
Cares about: nothing.
a land enters the battlefield — 1,560 cards in the game can cause this (Hall of Storm Giants is one).
When Hall of Storm Giants enters:
199 other cards care about it too. These are the ones with the most connections.