Your maximum HP just drops from 140 back down to 100. You don't die. Although that would be hilarious.
Thanks Warkupo.
Though the hilarity would be subjective I guess 
-H
I seem to recall, but haven't tested or paid much attention to it in a long time, that changes in your max hp basically "stretch" or "compress" your current HP so that the bar doesn't appear to move (the actual heal part of Dull Pain still moves the bar, of course). So if you're at 20/140 (14%), and Dull Pain wears off, you'll drop to 14/100 HP (still 14%).
Mm, I may have answered your question too quickly. Let me elaborate a bit:
When Dull Pain ends your HP is scaled back down to whatever it was before, in this case 100. Your current HP, in this case 20, is also scaled down to match whatever your current maximum HP is.
20 is roughly 14% of 140. 14% of 100 is... well, 14. So if you have 20 HP, and Dull Pain ends, your current HP will be set to 14 HP. So, while what I said about you not being able to *die* from Dull Pain expiring is true, I don't want to give the impression that you don't still have some repercussion from it fading.
Hmm interesting...
Looking at my "actual" numbers, I'd drop from 3500 to 2400 HP when DP wears off. I guess my only concern would be surviving those few seconds until it fires off again (giving me a nice heal)
Thanks for clarifying,
-H
I have done a search, but come up empty so far, so am resorting to the question...
What happens to your HP when Dull Pain expires?
I'm building an Invuln/StJ Tank with whom I'm having a LOT of fun at the moment, and am fiddling with mids for perma-Dull Pain. However the best I can do (without Hasten and without sacrificing Def) is a recharge of 125 seconds (5 second downtime).
The reason I went no Hasten, is the glowy hands, and the fact that I want to put DP on auto.
So for arguments sake, lets say I have 100HP. Dull Pain boosts that to 140.
Now, I fight a bit, and let's say I'm on 20 HP when the power expires. Will I die due to losing the extra 40HP, or will I remain on 20 HP, it's just that my max HP drops from 140 to 100?
Sorry if this is a daft question. I'm just trying to figure out how bad it is to have downtime on the power.
I'm aware that it is mainly used as a self-heal, as well as a HP boost, but I'm trying to build an invuln/regen tank and want to see how it plays out having the layered defence of invuln + massive regen + huge HP.
Cheers in advance!
-H