[Poruku]

What if we gave it something similar to vydel? Doing attacks with the weapon builds up charges (more on crit) and using a normal basic attack action when at max charges performs the special strike guaranteed. Make it also powerful/flashy enough to be a "oohhhh!" moment and you have a really cool system. In my opinion a purely %chance based system for this is pretty meh, and I think the cooldown is also unnecessary.

Alternatively, keep the cooldown, make the chance 100%.