mtg tergrid commander deck EDH Deck Tergrid, God of Fright 100 Magic Cards Custom Deck Discard Sacrifice Black 4/5 Tergrids Lantern Tergrid is one of those

Control decks usually operate on this axis of getting to a point where you have a bunch of lands in play and you're doing multiple powerful things that will draw you ahead of your opponent before they can do anything to you

It has an errata confirming the correction, so any character can be chosen, not just the opponents

Paste the code inside and click 'Redeem'

It makes sure your deck is consistent and complete, helping identify what your deck might currently be lacking, letting you refine your deck lists independent of playtesting

Here's a list of all the known MTG decks that contain Arena codes inside the box: The Core Set 2021 planeswalker decks include a code to get an MTGA copy of the deck too