Locust Swarm Based Spell

[lex90]

Im trying to make a spell after locust swarm that should look like this : There is a single unit created (with the locus ability --- ot sellectable/invulneraBLE) wich should attack units around it, without returning to the caster after a while --- and i dont know what to set in the spell so i can fix the 'attack and then return' thingy

 

[paskovich]

Locust works like units attack one enemy, than return. I don't see any option to ignore that...

 

[lex90]

thats not quite true they attack 2 or 3 (its actually they deal an ammount of damge) and then return