Kraum, Ludevic's Opus

Mana cost: {3}{U}{R}
Type: Legendary Creature — Zombie Horror
Power / toughness: 4 / 4
Set: Commander 2016 #34 (rare)

Flying, haste
Whenever an opponent casts their second spell each turn, draw a card.
Partner (You can have two commanders if both have partner.)

Kraum, Ludevic's Opus has 5 printings, first in Commander 2016 (2016). EDHREC ranks it #7,050 among Commander cards. It appears most in Kraum, Violent Cacophony decks (42 on EDHREC). 1 public deck on TCG runs it. It has 11 official rulings.

Legality

commander: legal
legacy: legal
vintage: legal
pauper: not legal
modern: not legal
pioneer: not legal
standard: not legal
brawl: legal

Public decks that run Kraum, Ludevic's Opus

Stalwart Unity - Commander 2016, led by Kynaios and Tiro of Meletis

Commanders that run Kraum, Ludevic's Opus most

Deck counts from EDHREC.

Often played with Kraum, Ludevic's Opus

Cards that show up in the same decks on EDHREC.

Rulings

2020-11-10: An effect that checks whether you control your commander is satisfied if you control one or both of your two commanders.
2020-11-10: One opponent must cast two spells for Kraum's triggered ability to trigger. Two spells from different opponents won't cause it to trigger.
2020-11-10: You can choose two commanders with partner that are the same color or colors. In Commander Draft, you can even choose two of the same commander with partner if you drafted them. If you do this, make sure you keep the number of times you've cast each from the command zone clear for "commander tax" purposes.
2020-11-10: Both commanders start in the command zone, and the remaining 98 cards (or 58 cards in a Commander Draft game) of your deck are shuffled to become your library.
2020-11-10: If something refers to your commander while you have two commanders, it refers to one of them of your choice. If you are instructed to perform an action on your commander (e.g. put it from the command zone into your hand due to Command Beacon), you choose one of your commanders at the time the effect happens.
2020-11-10: If your Commander deck has two commanders, you can only include cards whose own color identities are also found in your commanders' combined color identities. If Falthis and Kediss are your commanders, your deck may contain cards with black and/or red in their color identity, but not cards with green, white, or blue.
2020-11-10: Kraum's triggered ability can trigger only once each turn for each opponent.
2020-11-10: To have two commanders, both must have the partner ability as the game begins. Losing the ability during the game doesn't cause either to cease to be your commander.
2020-11-10: Once the game begins, your two commanders are tracked separately. If you cast one, you won't have to pay an additional {2} the first time you cast the other. A player loses the game after having been dealt 21 damage from any one of them, not from both of them combined.
2020-11-10: Kraum's triggered ability will resolve regardless of whether the first or second spell that a given opponent cast that turn has resolved, was countered, or is still on the stack. Notably, the ability will always resolve before the second spell resolves.
2020-11-10: Kraum's ability looks at the entire turn to determine which spell is a player's second spell. It doesn't matter whether Kraum was on the battlefield when the first spell was cast.