Does a player character who becomes a vampire gain the vampire's Legendary Actions?

Question

One of my players became a vampire by choice and according to the Monster Manual, "the character gains the vampire's damage resistances, darkvision, traits, and actions" (p. 298). Does that include Legendary Actions as well, or only the regular ones?

To my understanding, the answer is or should be no, because I am not sure as to how Legendary Actions qualify as actions per se, despite the name similarity. Also, legendary creatures are legendary for a creature, so a new vampire fledgling or spawn should no attain such powers that quickly. But, I would love some more valid input.

Answer 1

You do not gain the Legendary Actions.

The rules for legendary creatures from the intro to the Monster Manual state:

If a creature assumes the form of a legendary creature, such as through a spell, it doesn’t gain that form’s legendary actions, lair actions, or regional effects.

The primary utility of Legendary Actions is to help the DM balance the action economy between a single big bad monster and a large party of adventurers. Giving Legendary Actions to the adventuring party is just an generally bad idea for balance reasons, as the action economy already heavily favors a party of player characters, hence this rule.

This is also consistent with a plain reading of the rule and stat block. The "Player Characters as Vampires" sidebar reads:

the character gains the vampire’s damage resistances, darkvision, traits, and actions.

"Actions" is a specific section of the vampire's statblock:

Actions

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Multiattack (Vampire Form Only) [...]

[...]

This section details the actions the vampire can take on its turn in addition to the usual actions a creature can take on its turn. "Legendary Actions" is a different section of the stat block, and is an entirely separate mechanic from "Actions".

Answer 2

No, but even without Legendary Actions the PC will be very seriously overpowered

You already answered yourself in the question - the character gains the vampire's damage resistances, darkvision, traits, and actions". Legendary Actions are not in this list and in Vampire's stat block they are listed under their own separate heading, meaning they are their own separate class of abilities, different from regular Actions.

However, even without that the PC will still get all the following features: Shapechanger, Legendary Resistances, Misty Escape, Regeneration, Spider Climb, a bunch of weaknesses, out of which only Sunlight Hypersensitivity is a mechanically meaningful drawback and the others have impact on role-playing mostly. They also get Vampire's Actions: Multiattack, Unarmed Strike, Bite, Charm and Children of the Night. That is in addition to resistances (necrotic + nonmagical piercing, bludgeoning and slashing), 120 feet of darkvision unless they got that already and 18 in Strength, Dexterity and Constitution. All that is on top of all the abilities they already have since MM states that their game statistics don't change apart from gaining everything mentioned above.

This is going to make the PC seriously overpowered and will unbalance your campaign, hence the common practice of turning the character that becomes a vampire into an NPC. If you want to allow a vampire PC but make it a bit more balanced, the two alternatives I have seen used are either taking Vampire Spawn block instead of a regular Vampire (which will still make the PC pretty strong but not so completely unbalanced), since lore-wise, the character would rise as a vampire spawn rather than an already fully-fledged vampire, or changing the PC's race to Dhampir, which is quite well-balanced and gives the character the same flavour without making them overpowered.

MM in its paragraph about legendary creatures states:

If a creature assumes the form of a legendary creature, such as through a spell, it doesn't gain that form's legendary actions, lair actions, or regional effects.

Given the wording “assumes the form” it is unclear whether this is meant to apply to a character rising as a vampire or only to effects such as Polymorph but I think it doesn’t change anything either way as the rules on PC as vampires list clearly and explicitly all the features that the PC and Legendary Actions are not on this list.

Answer 3

It's not possible in rules as written for a PC to become a vampire. A vampire passes on their curse by killing a creature with its bite attack. When the creature rises they're a monster under the thrall of the vampire. The PC is now dead, and their body is under the control of the DM.

Bite. (Bat or Vampire Form Only). Melee Weapon Attack: +9 to hit, reach 5 ft., one willing creature, or a creature that is grappled by the vampire, incapacitated, or restrained. Hit: 7 (1d6 + 4) piercing damage plus 10 (3d6) necrotic damage. The target’s hit point maximum is reduced by an amount equal to the necrotic damage taken, and the vampire regains hit points equal to that amount. The reduction lasts until the target finishes a long rest. The target dies if this effect reduces its hit point maximum to 0. A humanoid slain in this way and then buried in the ground rises the following night as a vampire spawn under the vampire’s control.

Also once a vampire rises its personality is no longer that of the bite victim

Dark Desires. Whether or not a vampire retains any memories from its former life, its emotional attachments wither as once-pure feelings become twisted by undeath. Love turns into hungry obsession, while friendship becomes bitter jealousy. In place of emotion, vampires pursue physical symbols of what they crave, so that a vampire seeking love might fixate on a young beauty. A child might become an object of fascination for a vampire obsessed with youth and potential. Others surround themselves with art, books, or sinister items such as torture devices or trophies from creatures they have killed.

they are also bound to their grave

Chained to the Grave. Every vampire remains bound to its coffin, crypt, or grave site, where it must rest by day. If a vampire didn’t receive a formal burial, it must lie beneath a foot of earth at the place of its transition to undeath. A vampire can move its place of burial by transporting its coffin or a significant amount of grave dirt to another location. Some vampires set up multiple resting places this way.

These limitations are placed because vampires are very powerful.