Annoyed Altisaur
Creature — Dinosaur
Reach, trample
Cascade (When you cast this spell, exile cards from the top of your library until you exile a nonland card that costs less. You may cast it without paying its mana cost. Put the exiled cards on the bottom in a random order.)
It pairs a long neck with a short temper.
イラスト：
Modern Horizons 3#284アンコモン英語適正
裁定
The cascade ability triggers when you cast the spell, meaning that it resolves before that spell. If you cast the card exiled by the cascade ability, that spell will go on the stack above the spell with cascade.
When the cascade ability resolves, you must exile cards. The only optional part of the ability is whether or not you cast the last card exiled.
Countering the spell with cascade has no effect on the cascade ability.
You exile the cards face up. All players will be able to see them.
You don’t have to cast the last card exiled by a cascade ability. If you choose to do so, you’re casting it as a spell. This means that it can be countered, and appropriate abilities trigger (such as if that spell also has cascade).
If you cast a spell “without paying its mana cost,” you can’t choose to cast it for any alternative costs. You can, however, pay additional costs. If the card has any mandatory additional costs, you must pay those to cast the spell.
If the card has 
in its mana cost, you must choose 0 as the value of X when casting it without paying its mana cost.
The converted mana cost of a spell with cascade is determined only by its mana cost, no matter what the total cost to cast the spell was.