Bloodied
Monsters are dangerous creatures, if they weren't, then adventurers would be out of a job. Like any creature, though, a monster that is hurt and wounded becomes more dangerous, lashing out and unleashing their most powerful abilities at their attackers.
When a creature becomes bloodied, it is often a moment of realization. That the situation they are in is very dangerous and that the individuals they are facing off with must be dealt with quickly.
What is Bloodied?
A monster becomes bloodied when they are reduced to half their maximum hit points or lower. The aarakocra in the Monster Manual has 13 (3d8) hit points. Its hit point maximum is 13 and its bloodied value, half of its maximum, is 6 hit points.
When a creature becomes bloodied, this should be expressed to the players. If a dragon is struck by a mighty blow from an axe, you might describe the attack as "Your axe swings out battering into the dragon and breaking through scales. The dragon is breathing heavily as it bleeds from many wounds. It is bloodied."
What Happens?
When a creature becomes bloodied, a variety of different things can happen based on the creature. A dragon could immediately recharge, and then use its breath weapon. An ankheg could now deal acid damage when it is struck by a melee weapon as its blood sprays with each impact. Each creature will react differently to being bloodied, based on how they fight.
Once a creature becomes bloodied, they remain bloodied even after gaining healing that heal them above their bloodied threshold. They only stop becoming bloodied, or can reactivate a feature that happens when they become bloodied, once combat stops and they finish a long rest.
- Aura. Some creatures release an aura when they become damaged, though it needn't be a magical aura. A creature like the ankheg may have a 5-foot aura that only activates when they are hit by a melee weapon, their blood spraying out with each strike and damaging those who attacked them. Damage from an aura is typically a number of d6s equal to half their proficiency bonus, so an ankheg would deal 1d6 acid damage to anyone who hit them. If a creature already has an aura, it can either double in size or deal an additional die of damage.
- Damage. If the creature is an especially strong monster and relies on brute tactics like attacking and attacking harder, then when they become bloodied, they begin powering through and hitting harder than before. A creature with the Brute feature or something like the cyclops is an example of a brute who relies on their raw strength to smash through their enemies. When they become bloodied, they deal an additional die of damage on all their attacks.
- Extra Attack. Some monsters are fast attackers, striking out in quick succession. These types of creatures could be like the marilith or the sahuagin. When they become bloodied they gain an additional attack that they can take as a bonus action, this extra attack is typically their attack that they use the most, like a marilith's longsword attack instead of using her tail again.
- Movement. Not every creature will be focused on dealing more damage, instead, they may take this opportunity to begin fleeing. A creature like the Roc, might be more interested in an easy fight instead of potential death and is likely to flee once it becomes bloodied. As a reaction, the creature can move up to its speed away from any attacking creatures. This movement doesn't provoke attacks of opportunity. In addition, they can disengage or dash as a bonus action on each of their turns.
- Recharge. If a creature has an ability that recharges by rolling a d6 at the start of their turn, like a dragon's breath weapon or a mind flayer's mind blast, it immediately recharges and they can use this ability at the end of the current creature's turn using either their reaction or a legendary action. If they have neither action available, then the ability is only recharged. A creature tries their best to hit the creature that hit them, often ignoring a more tactical target, or targets, in favor of instinctively striking back at who hit them.
- Spellcasters. Those with a connection to magic become even more attuned to it during a fight, as the fight becomes more dangerous for them, they begin straining their bodies and grabbing on to more and more magic. While this is dangerous, it's not as dangerous as a party of highly skilled adventurers ready to bear down on them. The spellcaster immediately regains a number of spell levels equal to half their Challenge Rating. This means that if a spellcaster is a CR 12 creature, then when they become bloodied they regain up to 6 spell levels that can be turned into a single 6th-level spell slot, three 2nd-level spell slots, or any other combination of spell slots.
What Does NOT Happen?
When a monster becomes bloodied, it could be tempting to simply give them a higher Armor Class or more Hit Points. The point of becoming bloodied is that the fight is more dangerous, not that it necessarily takes longer. A creature that just regains hit points isn't a more interesting fight for the party as that could've happened behind the screen and they'd never notice it. When deciding on a creature's bloodied ability, it should be something that changes the combat or presents new options for the player so it isn't a static fight.
Who Should Have It?
Not every mook or minion is going to have a bloodied stage, especially since they might have so few hit points that they take a single blow and become bloodied. You might still announce to the group when a creature is bloodied, just as an expression of how hurt they are, but keeping track of a bunch of special abilities can slow down combat. Instead, you may choose one or two creatures in a fight, the bosses of that fight, and give them bloodied abilities.
Increase Danger
A creature that has a bloodied feature is inherently more dangerous than a counterpart without it. If the fight is already incredibly deadly to the party, like an ancient dragon taking on a team of level 10 characters, it might not make sense to give it one more ability to defeat the players. But an ancient dragon taking on a team of level 17 character will have a harder time fighting them, thus giving it an extra ability can be useful in balancing the fight.
Most bloodied features aren't going to increase the CR of a fight, though there are exceptions and it depends on what level the party is, especially if the bloodied value just increases a monster's damage. A high-level party may not notice when a low-level monster now deals an extra 1d8 damage on their attacks, but a low-level party will.
Why Should You Use It?
The bloodied feature was introduced in the 4th Edition of Dungeons & Dragons as a way to create more dynamic fights. Most creatures don't want to die, they don't throw themselves into combat, and they definitely aren't impassive about their fate. They may start yelling or screaming insults at the adventurers, hysterical as they give into their blood lust. They may start freaking out, lashing out with even greater power as their anger spurns them on.
Every creature has a fight or flight reflex, and giving creatures a bloodied feature is a way of bringing that mechanically into a game. If a creature is facing off against a party of adventurers, chances are they have been in fights before. Each one is going to approach fights differently, just as their body is going to react in ways to keep them alive, even if they aren't aware of it. Having a bloodied feature might be a safety reflex, where a dragon instinctively breathes their weapon after taking a nasty hit as a reaction to being struck, even if it was trying to properly plan out its breath weapon for the greatest effect and, on instinct, only hit the single creature that hit them.
Example Monsters
The following monsters are no different from the ones that appear in the Monster Manual except now they gain the bloodied feature below. Also, a monster's bloodied value is presented below.
- Aarakocra Bloodied 6
When the aarakocra becomes bloodied, it can use its reaction to fly up to its speed. This movement does not provoke opportunity attacks. - Aboleth Bloodied 67
The aboleth's mucous cloud is now filled with its blood. Any creature that ends their turn within 5 feet of the aboleth takes 2d6 poison damage. - Ankheg Bloodied 19
When the ankheg becomes bloodied, its chitinous armor is heavily cracked. A creature that hits it with a melee attack while within 5 feet of it takes 1d6 acid damage. - Banshee Bloodied 29
When the banshee becomes bloodied, it begins struggling to maintain its physical form and begins phasing in and out. Each time it is hit by an attack, it flickers out of existence momentarily and then reappears in a new position, this ability is out of its control. The DM rolls a d8 to determine what direction and then a d4 to determine how far away it reappears after being hit. - Behir Bloodied 84
When the behir becomes bloodied, it immediately recharges its lightning breath and then can use its reaction to use it. It must target the creature who made it bloodied and activated this ability if it uses the breath as a reaction. - Beholder Bloodied 90
When the beholder becomes bloodied, it immediately lashes out with its eye beams in a wild burst, this can be used as a reaction or the beholder can expend a use of one of its legendary actions. Each creature within 120 feet must make a DC 16 Dexterity saving throw. On a failed save, they are subjected to a random eye ray. - Bugbear Chief Bloodied 32
When the bugbear becomes bloodied, adrenaline begins pumping through it and becomes more dangerous. The bugbear deals an extra die of damage against the creature that bloodied it. - Demon, Marilith Bloodied 94
When the marilith becomes bloodied, they strike out with blistering speed. The marilith makes two additional longsword attacks when they take the Multiattack action. - Devil, Pit Fiend Bloodied 150
When the pit fiend becomes bloodied, its fear aura is now laced with evil energies. A creature that begins its turn within this aura takes 3d6 psychic damage. - Adult Red Dragon Bloodied 128
When the dragon becomes bloodied, it immediately recharges its fire breath and then can use its reaction to use it. It must target the creature who made it bloodied and activated this ability if it uses the breath as a reaction. - Empyrean Bloodied 156
When the empyrean becomes bloodied, a wave of radiant or necrotic energy (the empyrean's choice) washes out from in a 30-foot radius sphere centered on it. All creatures of the empyrean's choice must make a DC 15 Dexterity saving throw or take 55 (10d10) radiant or necrotic damage, or half as much damage on a successful save. - Fomorian Bloodied 74
When the fomorian becomes bloodied, it immediately recharges its Curse of the Evil Eye and, as a reaction, targets the creature that bloodied it. - Lich Bloodied 67
When the lich becomes bloodied, it immediately regains 10 spell levels that it can use to regain spell slots. - Roc Bloodied 124
When the roc becomes bloodied, it can use its reaction to fly up to its speed. This movement does not provoke opportunity attacks. - Vampire Bloodied 72
When the vampire becomes bloodied, it immediately recharges its Children of the Night ability and, as a reaction, use it.