So I was watching my girlfriend finish the Dragonborn DLC last night, and she is not the most skilled player, she mainly uses 2h and just swings away. I sometimes have to remind her to power attack, or to stop power attacking with every attack. If a fight is especially tough, she asks me when to block, bash, etc. But for the most part she is just swinging with no real strategy in mind. She's also level 46 and reset BOTH her primary skills (2h and heavy armor) at the same time, even though I told her to do one, get it back up, then the other (so she wouldn't be significantly weakened) and she forgot when they hit 100 and I was at work. AND she spent all the reset perks on skills she barely uses. She's in full ebony (enchanted from shopkeepers with good enchantments) and uses the helm of Clavicus Vile.

So now that the stage is set, let me tell you. She was using her Ebony Greatsword and started to lose ALOT of health, long before the final battle. She has the Ebony Blade, both as a backup after getting Disarmed during the Forbidden Legend quest, and for the occasional friendly she has to kill for a quest. She was getting owned. She then ran out of potions. I told her to use the Ebony Blade although it is much weaker than her Greatsword. I don't think she has killed that many friendlies for it... but MAN that thing saved her! That sword is really, really useful! I have never used a 2h build myself, so I had no idea how great it was. Is there any way to check how many boosts from friendly kills it's received?

Google is your friend

"This weapon starts with a 10-point http://elderscrolls.wikia.com/wiki/Absorb_Health. For every two such characters killed, the weapon's Absorb Health enchantment increases four points. Killing ten friendly characters maximizes its power at 30 points Absorb Health per hit."

Edit: Ah i misread, no i don't believe there is a way to check that, just when it's full as mephala will say so.

Basically, you're right. Also, OP, find a friendly NPC, equip the ritual stone, kill NPC with Ebony Blade, then revive them with Ritual Stone. Rinse and repeat to upgrade it to max.

Ebony Blade is pretty awesome. I've maxed out by slaughtering off the people in two settlements within Markarth area. (Both were mines actually. One mine was the one where you help them get rid of some Silver Blood thugs. The other had a Draugr problem). I did got the message from the Daedric Prince about it being fully powered...

What I don't get is... It don't work. Using it on friendlies ticks them off like normally...

Oh and I once got the Ebony Blade on level 4 on a Xbox character once and it is pretty awesome getting at a low level, though it'll count as a quest item since the only way to get it on a low level is by getting a follower to magically open the door and go through the talking cabinet, which is labeled the Whispering Lady, then tell the follower to pick it up.

You can do this as of 1.9?