mtg cards with mentor Seedglaive Price create a 1/1 white Monk creature token with prowess. Stormcatch Mentor | Bloomburrow MTG

While it's possible it could support brand new builds of Restore Balance or Living End that drop the cascade spells (and along with them the "no cards with CMC 2 or less" restriction), it may be more likely that Yahenni's Expertise finds a home in the existing build of Restore Balance (and maybe even Living End) as a way to cast the namesake cards when you happen to draw them naturally

With three mana, you can play plenty of great commanders, cast tons of mana rocks, and have access to all sorts of other ramp spells

Im not sure where itll end up in Pioneer, but itll end up somewhere

Its also just kind of Lier, Disciple of the Drowned with more colors, and some storm potential with a deck full of spells