The Weatherseed Treaty is a uncommon Enchantment — Saga card from Dominaria United (DMU), collector number 188. Current market price: $0.28 (foil $0.42), TCGplayer market prices via Scryfall.
Read ahead (Choose a chapter and start with that many lore counters. Add one after your draw step. Skipped chapters don't trigger. Sacrifice after III.) I — Search your library for a basic land card, put it onto the battlefield tapped, then shuffle. II — Create a 1/1 green Saproling creature token. III — Domain — Target creature you control gets +X/+X and gains trample until end of turn, where X is the number of basic land types among lands you control.