The more I leaf through the Monster Manual looking for material, the less interested I am in monsters that follow a straightforward brute profile (high Strength, high Constitution) and have no distinctive feature that gives them a reason to do anything other than run up and munch you. For this reason, the cambion deserves some attention. Even though the concept of the cambion, as a creature, isn’t that appealing to me (offspring of a fiend and a humanoid, naughty by nature), its particular combination of abilities and features is intriguing. This is not a straightforward monster. On the contrary, it offers more flexibility than most.
First, although its physical abilities are all very high, its two highest are Strength and Dexterity. The cambion is neither a stereotypical brute (Strength and Constitution) nor a stereotypical skirmisher (Dexterity and Constitution) but rather a shock attacker, optimized for moving fast and hitting hard, for quick and decisive battles rather than drawn-out slugfests. But it also has high Intelligence and even higher Charisma, meaning it has the option to talk its way out of a fight that’s dragging on too long—and so do its opponents.
It has proficiency in several saving throws, but of them, only Constitution is one of the big three—the ones that most damaging or debilitating spells require. It’s got a good enough Dexterity to compensate, maybe, but not Wisdom. So despite its other advantages, the cambion does have reason to be apprehensive around spellcasters, especially bards, sorcerers and wizards with a lot of mind-controlling or restraining spells in their repertoires.
The cambion’s social skill proficiencies include Deception and Intimidation but not Persuasion, so good-faith negotiation isn’t its style—against weaker opponents, it will bully, and against equal or stronger ones, it will try to outfox them. It’s also proficient in Stealth, which combined with its shock-troop ability profile indicates an aptitude for ambush.
Cambions are resistant to physical damage from normal weapons, along with cold, fire, lightning and poison. These resistances, combined with its high armor class, suggest a lack of concern with being struck by opportunity attacks. Since cambions can fly—quite fast, in fact—the tactic of hovering in the air, flying down to strike, then flying back up out of reach is feasible.
The cambion’s Multiattack comprises either two melee attacks (the only such attack listed in its stat box is spear, which it will use two-handed, since it’s not listed as carrying a shield) or two uses of Fire Ray. The spear’s damage edges out the fire ray’s, but barely, so the cambion is happy to attack at any distance. If its chosen target is fighting with dull iron, it can strafe him or her with its spear; if its target carries a magical or poisoned weapon, it can hurl fire from a safe distance instead.
The cambion can innately cast alter self, command, detect magic and plane shift (self only). The last of these is its escape hatch, which it uses when it’s seriously wounded (reduced to 32 hp or fewer). Command can be used to force an opponent to incur an opportunity attack by running out of reach (or to fall prone, but this is useful only if the cambion has allies that can follow up with their own attacks before the target gets back up). Detect magic isn’t useful in the midst of combat.
Alter self, at first glance, seems mainly to be how the cambion passes among humanoid society without being seen for what it is. (Horns, wings, tails and crimson skin have a way of setting people on edge.) But if an enemy of the cambion, while engaging it in melee, manages somehow to both corner and disarm it, it can cast alter self to sprout claws à la Wolverine and keep brawling, since it would attack with disadvantage if it tried to use its Fire Ray at melee range. Interesting question: Should it do an additional 1d6 fire damage if fighting with a melee weapon other than its spear? I would say yes, and here’s why: If you reverse-engineer the cambion’s attack, spell save and skill modifiers, you can determine that it has a +3 proficiency bonus. You can then determine that its spear is not a magic weapon: it has no bonus to hit and no bonus to damage. The fire, therefore, comes from the cambion itself, not from the cambion’s weapon, and so it should get that extra fire damage die even when it’s attacking with a different weapon, including natural weapons sprouted courtesy of alter self (which, incidentally, are magical, with an extra +1 to hit and to damage).
Finally, the cambion has Fiendish Charm, a simple charm person analogue that differs in two ways: first, the charmed target obeys the cambion’s commands, and second, a successful saving throw immunizes the target for 24 hours. Fiendish Charm is usable on only one target at a time, too slow for use in combat. But a cambion has only to see a target to charm him or her, and Fiendish Charm is not an attack, so a cambion can use this ability from hiding and remain hidden even if it fails. The only hitch is, it risks breaking the enchantment if it attacks its target. (A less important consideration is that its Intelligence isn’t high enough for it to “read” characters’ stats—it can only make educated guesses. It knows better than to try to charm a cleric, druid, ranger or monk, or an elf or hill dwarf of any class. Non-elven, non–hill dwarf bards, rogues, barbarians, sorcerers, warlocks and wizards are better bets. Paladins are a crapshoot; a cambion may go ahead and try, just out of contempt and to test its luck.)
So the questions that you as the dungeon master have to answer in advance are these: Why is the cambion there in the first place, what would it want from interlopers such as the player characters, and how badly does it want them dead? Whatever a cambion’s interests are, it will look to further them the easy way. If it can get your PCs out of its hair—or even get them to do its own work for it—by charming a couple and fast-talking the rest, it will. If the PCs are likely to be violently uncooperative, so be it. A single cambion can take on a whole party of level 1 or 2 PCs by itself, maybe even level 3 if there aren’t too many of them. Against intermediate-level PCs, it will need allies or minions.
A cambion that’s serious about killing your PCs will lay an ambush for them. While hidden, it will use Fiendish Charm against those within 30 feet whom it surmises to be promising targets who may cause trouble if not charmed. When it’s ready, it attacks from hiding with surprise, using its spear if an opponent is within reach, Fire Ray otherwise. Having already charmed one or more members of the party, it can command them, “Do not interfere!” as free communication on its turn, without having to use an action, and it can tell them to do other things as well as the fight goes on, as long as it doesn’t involve their coming to harm and thereby getting more saving throws.
Priority targets will include spellcasters, particularly fragile-looking ones; anyone wielding a magic weapon; and anyone within 60 feet who’s isolated from his or her allies. The cambion will fight from between 10 and 30 feet in the air, flying down to stab with its spear, then flying back up again, unless and until its target lands a couple of opportunity strikes; after that, it will shoot Fire Rays from the air instead. If any of its opponents has a magic weapon, it may cast command to order the opponent to drop the weapon, then fly down and snatch it up (yet another thing it can do in tandem with its movement and action). Of course, once it’s picked up the opponent’s weapon, it wields its own spear with one hand only. If it has allies or minions surrounding an opponent, it may cast command to order that opponent to flee, incurring a flurry of opportunity strikes. However, the cambion will only cast command against opponents it considers “charmable”; against anyone else, it’s likely to be a waste of an action, and the cambion does not want to waste time in combat. If it can’t dispatch roughly one opponent per round, it’s going to consider the whole fracas more trouble than it’s worth.
After one round of combat has gone by for each uncharmed enemy, if the cambion hasn’t defeated them yet, it starts losing patience and barking out orders to surrender (if they’re weaker) or offers to let them live if they give it what it wants (if they’re of comparable strength or stronger). It keeps fighting all the while, but it’s talking as it fights, and it stops fighting only if the two sides manage to come to a deal mid-combat. It will start talking even sooner if it’s moderately wounded (reduced to 57 hp or fewer) or if all its opponents have shown they have ways to hurt it badly.
The cambion’s fiendish parentage influences its alignment and determines how closely it keeps its word. The offspring of a devil will adhere strictly to the letter of any agreement it comes to, although it’s forever alert for loopholes that will let it subvert the spirit. The offspring of a demon will break its word the second it’s advantageous to do so. The offspring of a yugoloth will keep its word as long as it’s getting something it wants out of the deal, and no longer. The offspring of a succubus or incubus will keep its word as long as it amuses it to do so.
Cambions can be killed on the material plane, and their self-preservation instinct is strong. They’ll bug out with plane shift when they’re seriously injured, and they may even do so sooner if the fight is going badly for them and its opponents seem determined to fight to the death rather than make a deal.