mtg march of the machines art cards Set Booster Box – Keystone and Games March of the Machine -

As of this article, Pacifism has appeared in 25 different sets

All told the card is a little bit too good but it is generally not proactive, it does have plenty of counters and it is low key enough not to be as oppressive as the other cards that are as far above the power curve as it is

While all these decks have sideboards, you wont be able to access those cards without the learn mechanic

Here are the Kamigawa: Neon Dynasty Commander decklists "Upgrades Unleashed" and "Buckle Up"

The actual problem here is that you dont often want to use this on turn two on draw, because you might need to discard

The beauty of this combo is that all those Cursed Mirror copies have haste so they can immediately attack the table with a swarm of combat damage