How to Scatter-shot pierce missile attack?

Artillery AoE attack with 0-50 range?

you mean something like barrage or glaives?

@Mechanical Man he could use an ability like Cluter Rockets but that won't autocast unless he triggers it.

@Mechanical Man
I'd to make its normal piercing attacks to do like splash damage (something like that scatters) since the missile projectile art I used is a shrapnel explosion.

@deepstrasz - How I make it triggered in exact timing, the even of attacking of this unit and the cluster rockets?

@Battleborn a unit attacks/acquires a target->order unit to cast Cluster Rockets at position of target/attacked unit.