Most people played Sheoldred, the Apocalypse in their Grixis deck, but before our tournament, nobody played as many copies as we did. Looking over the Grixis decklists from before our Regional Championships, most people played either zero or one copy of the legendary creature in their main deck, with one or two in the sideboard, to have two copies in the 75. However, we instead played two in the main deck, with a third in the sideboard, and I was also pretty close to just playing three in the main deck.
I believe that this was one of the best decisions we made.
The previous consensus seemed to be that Sheoldred was bad in the mirror, but from our testing, we simply just did not find that to be the case. Rather, it was great on the play, but not on the draw. It was great on the play because, as we will get to later, the mirror match on the play is all about executing a tempo plan and getting on board quickly.
Sheoldred is a big threat that must be dealt with straight away, and doing so hastily forces your opponent to not commit onto the board themselves.