4e Cambions and Alu-fiends

Nice work!

Cambion

Ability bonuses seem appropriate, as do the skill bonus to Stealth. However, I would make the other bonus Perception rather than Thievery, considering the emphasis put on senses by the original PS Monstrous Compendium: “Cambions have keen senses and are never surprised.”

Traditionally, cambions are the offspring of a male tanar’ri (not necessarily an incubi) and female human, so I would change your Diabolic Heritage to Demonic Heritage, use the (demon) subtype, and make similar changes where appropriate.

You should note duration and range of the Unsettling Presence. Making it last until end of your next turn while requiring a Standard Action seems far too weak, but making it last until end of encounter seems well out of bounds for a racial power. I would recommend making it a Minor Action, and provide some additional interesting effect or perhaps make the effect last until the foe hits you. Compare to PH racial powers.

Alu-Fiend

The +2 to Cha seems a given but I’d change the second bonus from Dex to Wis. The PS Monstrous Compendium notes that “Alu-fiends have an innate intuition that warns them of impending danger 75% of the time,” and this way you avoid duplicating the halfling’s ability bonuses.

Unlike cambions, alu-fiends are to my knowledge specifically offspring of a succubus and male human, and I would note that they’re exclusively female. Since succubi have become devils in standard 4E I’m not sure which type would be more appropriate to a general user base, but if you’re playing in the traditional Planescape setting like me, I would again change Diabolic to Demonic Heritage and maintain succubi as tanar’ri (of course, this is a matter of personal taste).

Otherworldly Charm is too much, in my opinion – how about providing a reroll instead?

Vitality Drain reads vaguely to me – what does “the first time” apply to? Is it the first time in an encounter? If so, it seems more like a power than a feature. Is it the first time you bring any enemy down? If so, it seems vastly overpowered as the character easily heals up in a fight with minions. I would suggest ditching polymorph, making this trait the racial power, and write something akin to this:

Vitality Drain, Alu-Fiend Racial Power

You consume a share of the lifeforce of your foe as he crumbles to the ground.

Encounter

Immediate Reaction, Personal

Effect: When you reduce a foe to 0 hp or less, you can spend a healing surge and regain additional hit points equal to your Charisma modifier.

To replace the missing racial feature, how about this: Slow descent: Though your wings are too weak to fly, they can slow down a fall. Use half the falling distance when determining falling damage.

Hope you can use any of this feedback!