I know someone posted briefly about this item somewhere, but the skill talks about getting points for killing "Champion" monsters, but I think exactly what monsters fall into that class is hard to figure out on your own. Adding a one word description to all champion monsters so that it says champion on them would help a lot. From what I have found: it is basically all of the enemies can end up as expedition bosses.

What complicates figuring this out further is that when you have the buff, it appears as a small icon above your potions. This is different from Static Transferral or Branded Burst which have their own counters. Getting all of these skill counters to look and function the same would be nice for consistency.

The good news is that it definitely is working! Also, the skill appears to be providing a multiplicative damage bonus instead of additive (like all other nodes that I know of) is this intended? I checked because when I got the buff I took my damage, then stood still and waited until the buff fell off and got the new number, then did the math. I ended up with a 14% increase (it lists 15%) and I am fairly certain no other buffs were affecting it. If it IS intended as multiplicative of all material damage, it would be nice if you updated the tootip to say "+15% material damage added to base" or something like that.