I clearly remember Cambions existed in third edition, though I don’t know if they date from earlier than that. They’re only statted up in the Monster Manual.
Cambions are the offspring of devils and “depraved or unwitting” mortals. This wording is interesting because it specifically excludes violent rape. The mortal in question is either aware and willing, or being seduced by a “beautiful stranger” who later vanishes in the night. It fits the devil idiom in 4e.
It appears Cambions are usually raised by the mother, either in the World or in the Nine Hells. In either case they’re evil and vicious from childhood, taking on the worst traits of both parent species. I guess it’s technically possible for there to be a non-evil cambion, but the ones in the book aren’t them.
Cambions look like red-skinned humans with wings and horns. The book presents us with two varieties. They’re both Medium Immortal Humanoids (devil). The “devil” keyword marks them as official devils, and has a few rules attached: devils breathe and eat, but do not sleep. They are however not immune to sleep effects.
This guy is a Level 8 Brute with 106 HP. He has darkvision, resist 10 fire, speed 6, and a flight speed of 8 (clumsy). The “clumsy” keyword means he takes a -4 penalty to attacks and defenses while flying, so he only uses the wings to go from point A to point B. He wears mail and carries a flaming greatsword.
The hellsword’s basic attack is, well, the hell-sword which does physical damage and ongoing fire damage. When he charges he can make a sword attack against every enemy in range, and gains 5 temporary HP whenever he bloodies an enemy or reduces them to 0 HP.
The hellsword fights like a bowling ball, charging groups of enemies and then focusing on whoever is closer to being bloodied or taken out.
Cambion Hellfire Magus
This gal is Level 18 Artillery, and is all about setting things on fire. She possesses the same darkvision and speed as the hellsword, but her fire resistance is 15.
Her basic melee attack is with a quarterstaff, and as usual for artillery monsters it’s useless. Her main at-will attack is the Hellfire Ray, which targets Reflex, does fire damage, and knocks prone on hit. She can also use Soulscorch, an area attack that also targets reflex, and does both immediate and ongoing fire damage. That one recharges on a 5-6.
The hellfire magus also has a passive Soul Mantle power, which gives her +4 to AC and Reflex against ranged attacks.
Her tactics are simple: keep away and shoot fire. Her traits make it both desirable and difficult for PCs to close to melee with her.
Predictably, Cambions can be found hanging out with devils or with the sort of evil being who likes to hang out with devils. The suggested encounters are:
Level 8, four hellswords and a succubus. One happy family?
Level 18, 2 hellfire magi, a rakshasa noble, and 2 rockfire dreadnought elementals. A rajah and his advisors plus some summoned muscle.
Back in the 3e days it took me the longest time to figure out what made cambions different from tieflings. Both are descended from devils, right? Apparently the difference was that cambions were direct offspring, while tieflings were who knows how many generations removed from their fiendish ancestor. In 4e, of course, tieflings are humans mutated by a diabolic pact their distant ancestors made.
If you want to make a custom cambion, their “signature” traits are the devil keyword, the fire resistance, and the wings with their clumsy flight speed. Their attack powers seem to show a strong tendency towards fire, but there’s no specific fire power all cambions have.
Story-wise, I’d say people don’t really summon cambions despite them having the devil keyword. Rather, cambions arrive at a place by themselves and tempt other people into diabolism.