What makes an ability dispelable ?

[Goblioc]

Hello,

It may be a stupid question but : what makes an ability dispelable ? I looked for a true/false line in the stats but found nothing. It's not in the buff category either.
Why ensnare can't be purged ? Why inner fire can be ?
Is it hardcoded ?
So in order to have my custom spell dispelable, i need to base it on an already dispelable spell (and same for "not dispelable") ?

Thanks :

 

[Nichilus]

Ensnare is a physical spell. Physical spells are not affected by things like dispel or silence. It is hardcoded behavior (only ability that can change this is Channel).
You can either base the spell of something else or create a trigger that detects cast of all dispels and removes any physical buffs of your choice from targets.