Decorated Knight // Present Arms

Note that UnCommander generally follows regular Commander rules, so rule 13 in the Commander Rules prohibits effects from bringing objects from outside the game into the game by default. If you want to allow these effects to fetch certain objects, it needs to be negotiated in your playgroup.

Your original deck is the deck you started the game with.

To exchange your library with a deck you own outside the game, select the deck to exchange it with, then simultaneously put your library (all of the cards in it) outside the game, face down, and put all the cards in the chosen deck, minus any sideboard, into your library in any order. Note that Present Arms then makes you shuffle your library.

The cards in your previous library remain in the same order, and are considered as a deck outside the game. Those cards can be referred to by effects that specifically mention them being outside the game (not exiled).

The chosen deck you own outside the game must also be legal in the format you are playing. Cards in the chosen deck do not need to be within the same color identity as your original deck.

All cards from your original deck that are not currently in your library remain in the game as the library is exchanged with the deck.

Commanders do not change if you exchange your library with a deck. Any Commander of the new chosen deck is put into your library like the other cards in the deck.

If any effect restarts the game, all cards you own from all decks involved in the game become part of your deck as the game is restarted, see 719.2. in the official Comprehensive Rules. You still cannot change any Commanders.

To draw a card from a deck outside the game, put the topmost card of that library outside the game into your hand. Effects that care about drawing cards will count this. Note that Decorated Knight’s ability refers to your “original deck”, so if your library is exchanged multiple times, Decorated Knight’s ability will only draw you cards from the deck you started the game with.

Trying to draw a card from an empty deck outside the game does not make you lose the game.