I get 300% increased lightning damage on melee hit for 2 seconds on my spellblade and i think i dont have anything thats supposed to give me that buff. This also stacks infinitely. So if i hit 25 times in 2 seconds i get 7500% increased lightning damage.
I think it might be the “lightning rider” node because i noticed a big powerspike when i picked it up and its functionality is pretty similar. Its supposed to give 5% melee lightning damage for 4 seconds on melee hit.
Here is a screenshot of my stats and passive tree:
After attacking the target practice dummy for a few seconds i get between 6k and 8k increased lightning damage.
this is my skill tree:
I also took my gear off to test, but i still get the +300% dmg buff without my gear on.