The next spell you cast this turn can be cast as though it had flash. When you next cast a spell this turn, put X +1/+1 counters on up to one target creature, where X is the mana value of that spell.
The mountain will build your cairn of snow and ice and stone.
Casting Ride the Avalanche doesn't require a target. As you put the delayed triggered ability on the stack after casting your next spell, you choose the target creature, if any.
Random a card of Magic: The Gathering (MTG), but you can also roll the D20 dice, random a Planeswalker, have fun with the random rules and more.