Cheapest priced copy (Jumpstart 2022): $0.69 at Card Kingdom, near mint, their price list as of .
Marit Lage's Slumber 
Legendary Snow Enchantment · Rare · Modern Horizons · #56
Whenever Marit Lage's Slumber or another snow permanent you control enters, scry 1.
At the beginning of your upkeep, if you control ten or more snow permanents, sacrifice Marit Lage's Slumber. If you do, create Marit Lage, a legendary 20/20 black Avatar creature token with flying and indestructible.
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
2 printings · $0.69 to $3.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Jumpstart 2022 | 319 | Rare | $0.69 | — |
| Modern Horizons | 56 | Rare | $0.69 | $3.49 |
3 rulings from Wizards of the Coast
- 14 June 2019If you don’t control ten or more snow permanents as your upkeep begins, the last ability won’t trigger. No player may take any actions during a turn before the turn’s upkeep begins.
- 14 June 2019If Marit Lage’s Slumber leaves the battlefield before its last ability resolves, you won’t be able to sacrifice it, so you won’t create Marit Lage.
- 14 June 2019If you don’t control ten snow permanents as the last ability resolves, you can’t sacrifice Marit Lage’s Slumber.