You may look at the top card of your library any time. You may play snow lands and cast snow spells from the top of your library. Whenever another snow permanent enters the battlefield under your control, you may pay {G}, {W}, or {U}. If you do, put a +1/+1 counter on Isu the Abominable.

Whenever Marit Lage's Slumber or another snow permanent enters the battlefield under your control, 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.