What it does
A creature with "Partner with [name]" lets you have two specific commanders together in one deck, named explicitly on each card. When this creature enters the battlefield, you may search your library for its named partner, reveal it, put it into your hand, then shuffle. That tutor effect works anywhere—even in your 99—not just from the command zone.
The common confusion: "Partner with" is not the same as plain "Partner." Generic Partner creatures can pair with any other Partner creature, but "Partner with" cards can only be commanders together with their one designated partner. You can't mix a "Partner with" commander with a random generic Partner creature.
In Commander, this enables built-in two-commander decks (like Pir and Toothy, or the Brawlers' Guildpact pairs), expanding your color identity and giving you the search ability as a bonus when either is cast from the 99.
