Talk:Gragas/@comment-4922088-20151019044120/@comment-11218751-20151019225809

The bug is on, where Gragas can't cast it and the spell costs 0 mana.

The game perceives that you have already cast a but in fact the barrel does not exist, so that's why whenever anyone has the bug and hover over the tooltip of the ability, they will see something like "reactivate this ability to instantly make the cask explode".