Myrion, Glacial Sanctuary

When Glacial Sanctuary enters the battlefield,
each player may put an ice counter on up to one
target nonsnow permanent they control.
(Permanents with ice counters on them are snow.)
Other snow permanents are indestructible, have shroud, and can't be sacrificed.
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A marvel sheltering the ancient highlands, which saw
many soils and times, still bearing its architects' hopes.