I know it's already been seen on players, but i think it's new when coming to creatures:
I just battled Dmik King and there was his joker with -62/1000 vitality xD
I've checked all the circumstances: Dmik had -2k vit at that time and played with 68% pray power, so i guess the joker had life when the battle started, but the energetic influence killed it, and it didn't do anything in combat, it was just there, never attacked and couldn't be attacked.
maybe that needs some further investigation...

Nice. I knew you could get negative vitality but only on your global counters. I have no idea why it is this way ( I could speculate but I don't think I have a valid reason). Anyone else?

Interesting. Was it still attacking and being attacked? (was it Still a viable target?)

no, it didn't attack and couldn't be attacked, it was just there and did nothing (except for existing =D)

it was as if it was already dead, but there was no line in the log saying "joker DIES", because it was already dead when the fight started...does this make any sense ?

as far as the battle log is concerned, the joker never got mentioned, and after all the other creatures were dead, his picture still smiled at me with its less-than-zero vitality xD

I did this several times before =D
As far as I know(i dunno if I saw it wrong), it prevents your enemies from using dying as a target (and on some circumstances, strong, random, weak), as it would target the -VE creature, yet cannot hit it O_o

I would be interested in reproducing this.
What I want to test is if you can heal it so that it can get above 0 VE.

No.. it can't be healed.. it is no longer a valid target for any ability, I presume. At least I couldn't heal it last time I checked. I'll reproduce it with u if u want, though.