Howl of the Horde

If the spell being copied is modal (that is, it says "Choose one —" or the like), each copy will have the same mode. You can't choose a different one.

Howl of the Horde creates a delayed triggered ability that triggers when you cast your next instant or sorcery spell that turn. The raid ability creates a second, identical delayed triggered ability. Each of these will create a single copy of the next instant or sorcery spell you cast during that turn. If you don't cast another instant or sorcery spell during that turn, both delayed triggered abilities will cease to exist.

If the spell being copied has an X whose value was determined as it was cast (like Crater's Claws has), each copy will have the same value of X.