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 you control enters, you may pay {G}, {W}, or {U}. If you do, put a +1/+1 counter on Isu.

{1}{S}: This creature can't be blocked this turn. ({S} can be paid with one mana from a snow source.)

Affinity for snow lands (This spell costs {1} less to cast for each snow land you control.) When this creature enters, artifacts and creatures target opponent controls don't untap during that player's next untap step. Return three snow lands you control to their owner's hand: Return this creature to its owner's hand.

Changeling (This card is every creature type.) You may have Moritte enter as a copy of a permanent you control, except it's legendary and snow in addition to its other types and, if it's a creature, it enters with two additional +1/+1 counters on it and has changeling.

{2}: Target snow land you control becomes a 4/4 Elemental creature with hexproof and haste until end of turn. It's still a land. (A creature with hexproof can't be the target of spells or abilities your opponents control.)

Whenever you cast a creature spell, if {S} of any of that spell's colors was spent to cast it, that creature enters with an additional +1/+1 counter on it. ({S} is mana from a snow source.)

({T}: Add {W}.)

{S}{S}: This creature gets +2/+0 and gains indestructible until end of turn. Tap it. (Damage and effects that say "destroy" don't destroy it. {S} can be paid with one mana from a snow source.)

When this creature enters, search your library for a snow land card, reveal it, put it into your hand, then shuffle. This creature gets +1/+0 for each other snow permanent you control.

This spell costs {X} less to cast, where X is the greatest power among creatures you control. {T}: Add {G}{G}. You gain 2 life. Whenever a nontoken creature you control enters, put a +1/+1 counter on it and draw a card.

Flying, vigilance {T}: When target creature other than this creature dies this turn, return that card to the battlefield under your control.