There are two big reasons to run these cards: Firstly, 5 manas the going rate for an extra turn with no strings attached
He also owns a PSA 10 First Edition Charizard which he purchased from Gary Haase for $150,000 (116,129 / 138,021) in 2020
However, I want to acknowledge the following rule for the Commander format: Rule 13: Abilities which refer to other cards owned outside the game do not function in Commander without prior agreement on their scope from the playgroup. Karn is a really good card for any 60-card format because you are allowed a 15-card sideboard from which you can pick cards that are "outside the game." However, in Commander, there are no sideboards or wishboards
This effect doesn't target Digimon in breeding areas
[1] Japanese cards used to be distributed in all OCG territories, though this has since ceased and are now only sold in Japan, by Konami of Japan
It should be noted that counterattacks don't care if your own attack power is halved or whatever, since they work off the enemy's attack power