create a dummy at the position of the caster with model size 1 or bigger (missle art and spell art (the rocket) gets bigger if u change model size) and give it a spell based on storm bolt or sumthing with the missle art as that rocket and change damage ofcourse. give that spell to the dummy and make this trigger:
events: unit casts a spell conditions: ability being cast is equal to 'that spell u click on with the caster' actions: create 1 'dummy' at positon of casting unit unit - order last created unit to 'human mountain king - storm bolt' random unit within 900 range of casting unit
then u dont need a spell but a dummy unit with the model of a rocket to move to the position of the unit (so if he walks away it also misses) and if the dummmy leaves a rect centered at the positon of the casting unit with size 2000x2000 (convert point with size to rect) kill the dummy
then u dont need a spell but a dummy unit with the model of a rocket to move to the position of the unit (so if he walks away it also misses) and if the dummmy leaves a rect centered at the positon of the casting unit with size 2000x2000 (convert point with size to rect) kill the dummy