This is not a skill they will spam or anything like that. It will be a one-time use skill except in some rare cases. A boss or two might get it and in that case it would recharge after a certain amount of time. Previously some lightning skills would cause silence randomly, but I didn't like that implementation. However it can still randomly interrupt your spell.

The mob will check if you're casting and try to interrupt your spell, and it will also silence you for about 5 seconds.