edhseer Commander synergy, explained
Instant
Mana cost: {2}{U}
For each spell and ability your opponents control, counter it unless its controller pays {4}.
on-cast —
Causes: counter a spell.
Cares about: nothing.
an instant is cast — 3,931 cards in the game can cause this (Whirlwind Denial is one).
When Whirlwind Denial is cast:
427 other cards care about it too. These are the ones with the most connections.
anything is cast — 31,128 cards in the game can cause this (Whirlwind Denial is one).
When Whirlwind Denial is cast:
5 other cards care about it too. These are the ones with the most connections.