Guild Wars 2

I just entered the story mission “A Tangle of Weeds” I was given the sword Caladbolg to do the mission with. I was looking over the skills of the sword when I noticed some have a special icon on them in addition to the casting time and cooldown time.

It looks like a water jug or a gord.
The Daybreak Blade and Flashing Arc (both skill1 attacks) have 1 of whatever this symbol is of.
Skill 2, Electrolyze, has 1
Skill 3, Skyfall, does not have the icon
Skill 4, Twilight Crush, has 5
Skill 5, Maelstrom Strike, has 1

I know the thief class has stamina but I think that icon is a star or asterisk.
I’m a mesmer and from what I can tell this symbol does not seem to affect anything.

Any one know what it means?
Iv yet to actually do the mission so maybe the mission will tell me, But I doubt it.

Also as a mesmer, my clones use the sword, not only do they use several of the attacks the sword has, not just the skill 1 auto-attack, but they actually deal damage with it.
donno if thats a bug or what but its sweet.
Edit: Just noticed I lost my shatter powers, thats probably why clones deal damage.