edhseer Commander synergy, explained
Instant
Mana cost: {U}{B}
Look at the top two cards of target opponent's library. Exile one of them face down and put the other on the bottom of that library. You may play the exiled card for as long as it remains exiled, and you may spend mana as though it were mana of any color to cast that spell.
on-cast —
on-cast — sets the top of a library
on-cast — taxes the table
Flashback {1}{U}{B}
Causes: exile a card.
Cares about: nothing.
anything is exiled — 2,497 cards in the game can cause this (Siphon Insight is one).
an instant is cast — 3,931 cards in the game can cause this (Siphon Insight is one).
When Siphon Insight 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 (Siphon Insight is one).
When Siphon Insight is cast:
5 other cards care about it too. These are the ones with the most connections.