This lets you play your entire hand and then draw back up, and it scuppers any immediate plans your opponents had placing their ambitions out of reach
In a stalled-out late game, trading in a token for constant reanimation is excellent
Peeking at the top of your library and casting Merfolk from there is a nice effect, and tacking on to create a 1/1 Merfolk is a tasty boon
You can still play him in Commander, though, if you want all the other players to suffer flashbacks and then turn on you in fury
Alternatively, you can win with Felidar Sovereign or Angel of Destiny, which will win you the game if you have a certain threshold of life, something easily done with how much life can be gained
The replacement effect from Agate Assault's first mode will exile the target creature if it would die this turn for any reason, not just due to lethal damage