Magus of the Order

{G}, {T}, Sacrifice this creature and another green creature: Search your library for a green creature card, put it onto the battlefield, then shuffle.

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Commander Legends

{G}, {T}, Sacrifice Magus of the Order and another green creature: Search your library for a green creature card, put it onto the battlefield, then shuffle your library.

If Magus of the Order becomes nongreen, you can still activate its ability by sacrificing it and a green creature.

Once you declare you're activating the ability, players can't take any actions until you've finished doing so. Notably, opponents can't try to remove Magus of the Order or green creatures you control to stop you from activating the ability.

You can't sacrifice additional creatures to search for more green creatures.