Criolex, First of the Frozen

When Criolex, First of the Frozen enters the batttlefield, tap all other non-snow permanents. They don't untap during their controller's next untap step.
{3}{u}: Draw a card. Activate this ability only if you control seven or more snow permanents.
"We are kings in this frozen paradise, Xarion. Why do you wish to desecrate it with fire? The Frozen God will not allow it, and as his First neither will I!"