How does Fulmintis recover EP?

The passive doing this is called Electro Stash, and it turns crit rate into a resource stat. On most DPS units crit is just damage. On Fulmintis, every point of skill crit chance is also EP income, which means gear and buffs that look like pure offence are quietly paying for your next cast.

That makes multi-hit skills the good ones to spend on. Lightning Blade Storm dashes at the target and chains consecutive slashes, the Q ability is a rapid barrage of strikes, and Lightning Blade Impact fires two Electric Blade Shock Waves when you hold it to enter Aim Mode. Each of those puts several separate hits on the board, and each hit is another roll that can pay out. A single big hit gives you one chance. A barrage gives you many.

Lightning Blade Storm runs on Energy, not EP. It spends Energy on the slashes and finishes with a Spinning Slash for 26 Might damage when Energy runs out or you press the skill button again. The EP the passive hands back is a separate pool, so the Storm draining itself dry does not cancel out what your crits are returning.

Pushing crit rate up on purpose

Enhanced Lightning Blade is the lever. The E skill coats the blade in electricity and raises skill CRIT rate by 25% for 20 seconds, so that window is both your damage spike and your refill window. Open with it and dump your skills inside the 20 seconds rather than trickling them out afterwards. Fulmintis also carries a base physical attack of 130, one of the highest in the game, which is why it sits in the DPS role and why the crits it does land hurt.

What a crit buys besides EP

Crits on Lightning Blade Impact inflict Paralysis on the target for 1 second, so the same buff window that funds your EP is also your lockdown. Fulmintis is a Lightning unit and several of its abilities paralyze, including the ultimate. Thunder Lance has a base power of 180, hits targets in a straight line and leaves them paralyzed.

One thing here is not crit-driven. Every three consecutive hits during Lightning Blade Storm increases the final Spinning Slash damage by 100%, and that counts hits, not critical hits. You want the Storm to stay connected regardless of how the crit rolls go.

Not settled: The trigger is written around skills, so whether a critical hit from anything other than a skill pays out the 4 EP is not settled.