It's quite the staple in Vintage, too, for black-heavy decks that want to dig deep for their combo pieces
Pick a template (Modern, Vintage, Mystical Archives, etc.), then change anything: name, mana cost, type line, rules text, power/toughness, art, artist credit
You open and keep all cards in those packs, which become your pool. Any number of players can participate in a Sealed deck event and there's a lot of variance depending on how lucky you are
Bladegraft Aspirant Remember what I was saying earlier about equipment decks being really close to having enough tools to be playable
Copies of Hellish Rebuke that weren't cast will give opponents permanents the ability, but that ability won't do anything because no player cast that copy of Hellish Rebuke