The skill I forgot the name of says that there are 20 stacks of it. The thing that says bigger targets give more stacks.

This skill only worked for a short time when the Ragnar was added, if I remember correctly, sometime around april last year. Then there was a patch and the skill either did not work at all, or as of now, gets just 1 stack. 4 skills now give 4% damage. OP stronk

At level 4, it says 4% damage per stack. I assume it applies to skills not just weapons. so, 80% damage at 20 stacks is something rather very strong - if it works again in full.