Does a subsequent charm effect override a previous one?

Question

In a recent session, I was confused about how multiple charm effects would interact with each other:

A vampire used its 'Charm' ability to charm a PC. It reads (paraphrased):

The target must succeed on a saving throw or be charmed by the vampire. It takes the vampire's requests in the most favourable way it can. It can repeat the saving throw if the vampire or its companions harm it. Otherwise, the effect last 24 hours or until the vampire is destroyed, is on another plane of existence, or takes a bonus action to end the effect.

Another PC then decided to attempt to wrest control back from the vampire by casting crown of madness on their friend. it reads (paraphrased):

The creature must succeed on a saving throw or be charmed. The charmed target must use its action before moving on each of its turn to make a melee attack against a creature other than itself that you mentally choose. The target can act normally on its turn if you choose no creature, or none are within its reach.

At the time, I ruled that both effects would take place simultaneously. This meant that Crown of Madness took effect first, and the vampire's charm afterwards.

Was this the correct ruling? Can a creature be charmed twice? Or does one charm effect override the other?

Answer 1

Charms don’t override/preempt each other unless that is called out in the rules

The quick answer is no — abilities or spells that impose the charmed condition don’t cancel previous charmed conditions. They can be in effect at the same time.

The answers to this question covered some of these charming rules

One exception is in the case of harpies, once a target is charmed by a given harpy, other harpies cannot charm the creature.

Charms are not all equal

Things get complicated because there is not a single “charm effect.” Various spells or abilities which impose the charmed condition (many of which are called “charm” or include the word in their name) actually impose very different sets of effects (See below).

For example, succubus can command a humanoid affected by her charm ability, while charm person only makes the target regard the caster as a “friendly acquaintance.” In general, the succubus’ commands would take priority over the request made with the benefit of Charm Person.

Charms in direct opposition

The exception to the above is if the command directly contradicts an effect of the other power, or contradicts the charmed condition, for example, if the succubus orders its thrall to attack a wizard who charmed the same humanoid. The charmed condition precludes this (see Appendix A: Conditions, PH, p.290).

In that case, the DM may rule that a contest is in order (See Contests, DMG, p 238) or may rule that the charmed condition precludes the action.

Crown of Madness vs. Vampire Charm

In the question’s particular case, the caster of Crown of Madness could maintain control the charmed character as long as the caster meets the requirements of the spell. That is, choosing a creature for the charmed PC to attack before moving on the first round (which might necessitate the PC attacking an ally) and “using his action to control the target” on subsequent rounds (PH p.230).

Also note the vampire’s effect might outlast Crown of Madness. The spell would persist while the caster’s concentration lasts, up to 1 minute. After that, the vampire’s charm, which lasts 24 hours, would still be in effect.

If the caster ordered the charmed PC to attack the vampire, then that would be a Contest as described above.

Differing Charm Effects

Here are a few charm effects for reference. There are a lot of subtle differences, so you have to be aware of the specifics to determine how they would interact.

Crown of Madness (PH p.229):

The charmed target must use its action before moving on each of its turns to make a melee attack against a creature other than itself that you mentally choose

Vampire (MM p. 297):

the target isn’t under the vampire's control

Charm Person (PH p. 221)

The charmed creature regards you as a friendly acquaintence.

Dominate Person:

While the target is charmed, you have a telepathic link with it...You can use this telepathic link to issue commands...

Succubus (MM p. 285):

The charmed target obeys the fiend’s verbal or telepathic commands.

Harpy (MM p.181):

While charmed by the harpy, a target is incapacitated and ignores the songs of other harpies.

Answer 2

Not sure why people insist there's a contest.

1. Crown of Madness says, you have to make a 'melee' attack and that attack must happen before the move. If the vampire is out of 'reach' of a melee attack as would be with 99% of cases the person would behave normally as per the wording of Crown of Madness.

2. An active condition imposed by two parties can't negate each other without explicitly saying so.

While charmed you can't attack the charmer...period. "Can't!!" For better or worse, treat Crown of Madness like Dominate Person. (Historically they have the same mindset.) Dominate Person says "You can issue commands to the creature while you are conscious (no action required), which it does its best to obey." Key point being that it does its best. So if I were to say Crown of Madness or Dominate Person on someone and tell them to attack another creature that charmed it, it would receive the command, but it couldn't complete the attack. Essentially the order fizzles. In crown of madness case, treat this as there is no target within range. As such in Crown of Madness' case, the target would get to behave normally which could lead to it following the vampires orders. Sure in the example the vampire is definitely a valid target, but the person "can't" attack him. Period! Why, because magic and the 'charmed' condition says so!

Answer 3

The charmed condition (which both of these effects create) can certainly be in force by 2 or more creatures simultaneously. All it does is (PHB p.290):

A charmed creature can't attack the charmer or target the charmer with harmful abilities or magical effects.

The charmer has advantage on any ability check to interact socially with the creature.

That just means there are two creatures that the charmed creature can't attack and who have advantage on social interactions.

In addition, whatever the vampire requests the charmed person will try to accommodate.

The Crown of Thorns effect would create a contest (p.161) if the person was ordered to attack the vampire. Probably Charisma (Persuasion) or (Intimidate), if the caster won the vampire would be attacked, if the vampire won it wouldn't.