Once again, how did I die?

Clearing maps, no deaths for 8-10 maps, everything smooth, go into a deadly boss map because im feeling confident.

Turn a corner, get 1 shot, lose my 1 portal...

I wonder to myself... how in the world did that happen because I have been doing so great.

I try to look at any mods on the mob that killed me... I cant because I'm dead.

I try to see any ground degen... nothing.

All I see is a random tentacle that appeared to come from the ground.

So... I ask again. How did I die? How did I lose my map that I prepared for?

62% evasion
17% phys damage reduction
68% elemental damage reduction against hits
48% deflect
40% prevented deflection

I get hit for either 5-10% of my life... or my entire life bar at once.

I would just like to know WHAT kind of damage is killing me, and how hard the hit was.

This is so i can either...

A. Report a bug about tentacles doing 100X the damage they are supposed to be doing?

B. Prepare my character in a better way to avoid taking large hits from the damage type that 1 shot me.

But... I cannot do either of those things because I have NO INFORMATION.

"X has been slain." Doesn't give me the information I need to improve my character or report a bug.

oh i forgot my 50% capped block as well.