edhseer Commander synergy, explained
Battle — Siege // Creature — Dinosaur
Mana cost: {1}{G}
(As a Siege enters, choose an opponent to protect it. You and others can attack it. When it's defeated, exile it, then cast it transformed.)
When this Siege enters, look at the top five cards of your library. You may reveal a permanent card from among them and put it into your hand. Put the rest on the bottom of your library in a random order.
triggered — searches a library
Trample
Whenever you cast a spell, this creature gains indestructible until end of turn.
triggered — grants a keyword
Causes: nothing.
Cares about: a spell is cast.
a battle enters the battlefield — 81 cards in the game can cause this (Invasion of Ixalan is one).
When Invasion of Ixalan // Belligerent Regisaur enters:
a battle is cast — 100 cards in the game can cause this (Invasion of Ixalan is one).
When Invasion of Ixalan // Belligerent Regisaur is cast:
235 other cards care about it too. These are the ones with the most connections.