ToME: the Tales of Maj'Eyal

I'm probably misunderstanding something, but when I was playing a skirmisher and got the fire dragon shield (30% chance flame breath on block) I started doing other breath attacks. Fire would proc on block, but when attacking in melee I would sometimes breath sand, acid, etc (I believe I even roared once). I'm not aware of any other equipment that would do that. I loaded the save and it no longer seems to happen even though I'm still using the shield. I only clearly remember it happening in Dreadfall.

Attacking in melee?
You can not use your sling to do normal melee attack, nor your offhand shield (unless you are using talents that use shield attack)
So, as you have no viable weapon for bump attack, you are using your hand to attack.
And your hand uses glove to attack. Different gloves can give you things like breath sand, acid, etc, and many other skills.
If you turn on 'Always show glove combat' option, you can see your glove properties.
Anyway, it is not a good idea for skirmisher to do bump attacks.