Momentus Difficulty issues

I just took out a momentus on difficulty 5. When it died it didnt drop anything cool, and it said Overall difficulty 4. I hadnt died through the fight, nobody was helping/watching, why did it count as difficulty 4?

Did you spawn the Momentus, or was it already there?

I think Momentus was trying to insult you. Don't take it personally, he's just a bad loser .

Nobody else hit it. It spawned far out in the wild by my gold farm and I saw it spawn originally.

If it took any other damage (drowning/suffocation/cactus/another mob hitting it/etc.) that will lower the difficulty.

Generally speaking your effective diff. will usually end somewhat less than your original one. Mostly caused by, as others mentioned, it taking more damage. Even a flaming sword can achieve this, or Momentus not being able to fully reach you ("warning, that mob has trouble reachign you"), etc.

I more than often fight these at 8, die a lot and end up with an eff. difficulty of 7 or sometimes 6.

Do poison potions count? One mighta hit it

Could me, I assume as much but I'm not fully sure. I do know that throwing TNT at it can cause this to happen

Next time I will try without a poison potion.