This obese demonic creature appears as massively cerebral baby, it's skin stretching to almost the point of bursting. Stunted, fleshy "wings" protrude from a layer of backfat. It's whole body roil of this round demon, as it improbably flies towards you.
Corpulent Bomber (Level 4 Brute ~ XP 175)
Small immortal humanoid (demon)
_____________________
Initiative +1
Senses Perception +10
HP 59; Bloodied 27
AC 14
Fortitude 15 Reflex 14 Will 12
Speed flight 6 (clumsy)
Immune poison, disease; Resist 5 acid, 5 cold, 10 fire; Vulnerable 5 silver
_____________________
Volatile Immediate reaction, when first hit by attack. Each round roll 1d6, if 5 or 6 corpulent bomber falls to 0 hit points and dies.
Death Bomb Immediate reaction, when reduced to 0 hp; encounter) * (Element), Zone. Close burst 2; +15 vs. Reflex; 7d6+4.
Unstable Any attack that deals at least 15 damage to corpulent bomber reduces it to 0 hp.
_____________________
Alignment Chaotic Evil
Languages Abyssal
_____________________
Str 9 Dex 8 Wis 9
Con 20 Int 11 Cha 5
~
I suspect there is a better way to word Volatile. Further it seems the trend is to have higher ability score in 4e, but I'm not sure...