A Strange Occurrence...

I am not sure how to explain this, but here it goes.

First, I am running Maria Jenkins’ missions with my SG mate's Defender. My character is my 47 lvl Electric Armor/Energy Melee tanker. My first mission is taking out Infernal and his minions.

While battling the first few spawns I noticed a green icon pop-up where my other power icons are, this had a shield and a cross. I had never seen that before on this toon. I thought it was something similar to the Invulnerability power icons. When I clicked on it, it said, "Invulnerable." Wait. What?

I do not have that power ability nor did my teammate. Therefore, I ignored it at first. However, it appeared again and even double stacked alongside my double stacked Damage Resistance from Might of the Tanker. This happened all during the night while I played in Maria's story arch. I looked through my power's enhancements to find if anyone could actually make my tank invulnerable. None showed anything.

The only thing I can think of is that MoT's proc has something to do with it. Not that I am complaining here, far from it, I like the idea that this happens. I would just like to know where it came from and how.

Has anyone faced this before?

Close proximity to Behemoths (big CoT demons) increases their defense and acc, this effect shows up on your active powers display using the invincibility icon IIRC.

http://paragonwiki.com/wiki/Circle_of_Thorns#Behemoth

Many other defensive powersets will do this as well--for example, fighting against SR or SD-using foes.

Basically the icon is saying your are withing range of their [Invincibility] power and you are buffing their accuracy and defense.

Sucks when you're in a team full of melee. It stacks fast.

It is funny to see Mage bosses drop faster than Behemoth lts, though.