Hello forums
Known this for a while now and thought I would share this tid bit of info today. Applies more so to pure chaotic and divine magic users who don't use any melee weapon at all. Also applies to those who land a parry but forget to switch to their melee weapon.
If you land a parry and immediately cast your great combustion/wog, you receive a bonus damage!
Also applies to casting these spells when behind them. The damage, as with backstabs, is less than the parry damage but you still receive a bonus.
Wearing Hornet ring does not increase the damage.
The damage modifier is around 20% increase for the parry.
For pvp this knowledge can be useful when facing say a tank greatsword user. He will assume you will keep GCing him and attempt to tank the GC while stunning you into submission. Rarely will he expect you to parry him as you do not have a weapon out in your right hand!
Just another tactic to consider