Applying (adding) an effect on hit.

To make your creature receive damage with an effect, use - Characters\Creatures\Necropolis\AlternativeUpgrade\DeseaseZombie-arena-hit.xdb

To make it deal damage with an effect, use - Characters\Creatures\Necropolis\AlternativeUpgrade\DeseaseZombie-arena-attack00.xdb

To speed up the visual effects debugging process, I recommend adding the "stir00" action to your creature. If it already exists, temporarily assign the attack or damage action to it, depending on the action being debugged. This can be triggered simply by hovering the cursor over your creature!