edhseer Commander synergy, explained
Land
This land enters tapped unless you control a Mountain.
Add {R}.
activated {T} — adds 1 mana
Add {R}{R}. If any of that mana is spent on a creature spell, it gains haste until end of turn.
activated {R}, {T}, Exert this land — adds 2 mana
activated {R}, {T}, Exert this land — grants haste
Causes: nothing.
Cares about: nothing.
a land enters the battlefield — 1,560 cards in the game can cause this (Arena of Glory is one).
When Arena of Glory enters:
199 other cards care about it too. These are the ones with the most connections.