D&D Monster Monday: Oni
You regain your senses after the torrent of frostbite subsides. Your armor is frozen and your muscles are numb but you press forward in hopes of cutting down the oni. It hauntingly swoops into the air and with a flourish carves you to bits with its magical glaive – laughing as you perish.
Like the minotaur which we’ve talked about in a previous D&D Monster Monday, the oni is a creature spurned from real-world mythology. They are supernatural ogres in Japanese folklore and this origin carries over into their D&D creature statblock.
As a D&D 5e creature they deal some savage burst damage and have a hearty helping of survivability. They’re deceptively mobile for such large creatures and utilize a reach weapon to the frustration of short-ranged front-line characters.
Think of oni as “the monsters under the bed”. They’re the subject of children’s stories typically to make the children behave. In the stories that human children are told, oni find babies and young children extremely delicious.
In the Forgotten Realms though these monsters are real. They seek out children and adults alike to abduct and eventually devour them. This is similar to ogres. They desire flesh for sustenance and they’ll kill or capture people to satiate their hunger.
However, oni are magical creatures. They can cast spells and are in tune with the arcane. Oni are particularly excellent shapeshifters and can change their form at their leisure.
Their shape-shifting abilities allow oni to infiltrate an unsuspecting town of humans and blend right in. They can stalk their prey or befriend a group of small children and use their relationship as leverage to take them away and eat them for dinner.
Besides seeking flesh, oni have a taste for luxurious and magical items. They crave wealth and luxury and will serve a higher power if they can offer an oni either or both of these things.
Oni’s Stats and Abilities
You can find the oni statblock in the Monster Manual (MM) on page 239 for reference!
Size: Large Giant
AC: 16 (chain mail)
Hit Points: 110 (13d10 + 39)
Speed: 30 ft., fly 30 ft.
STR: 19 (+4)
DEX: 11 (+0)
CON: 16 (+3)
INT: 14 (+2)
WIS: 12 (+1)
CHA: 15 (+2)
Overall I’d say that oni have it pretty great in the ability scores department. Their lowest ability is Dexterity which isn’t even negative. They have a +4 to Strength and +3 to Constitution which makes them a beefy melee creature, but their spellcasting abilities do not suffer because of this.
Their AC is solid at 16 and they have an average-sized health pool for large creatures at CR 7. However, I’d still consider them very solid defense-wise as they have 30 ft. of flying speed. This allows them to hover above enemies that are melee-focused and avoid any sort of nasty spells that would affect the ground below them.
Resistances, Immunities, Saves, and Skills
Saving Throws: Dex +3, Con +6, Wis +4, Cha + 5
Skills: Arcana +5, Deception +8, Perception +4
Senses: darkvision 60 ft., passive Perception 14
Languages: Common, Giant
This has been the first creature in quite some time that we’ve gone over that’s had any bonuses to saving throws, not to mention 4 of them! The only saving throws that oni don’t have a bonus on are Strength and Intelligence which they have a +4 in and +2 in respectively. Not to mention that these are two of the least-used saving throw abilities in the game.
I mentioned before that oni are typically deceitful and will manipulate people while disguised as humans or other humanoid creatures. The +8 Deception helps quite a bit with this type of tactic.
+4 in Perception gives them a passive Perception of 14 which is above average and can help them spot enemies trying to sneak up on them. The bonus to Arcana feels like a flavor thing more than anything, but it may come in handy.
Darkvision is always a plus! This is probably a trait passed on from their distant relationship to ogres.
Abilities and Traits
Innate Spellcasting. The oni’s innate spellcasting ability is Charisma (spell save DC 13). The oni can innately cast the following spells, requiring no material components:
At Will: darkness, invisibility
1/day each: charm person, cone of cold, gaseous form, sleep
Magic Weapons. The oni’s weapon attacks are magical.
Regeneration. The oni regains 10 hit points at the start of its turn if it has at least 1 hit point.
There’s a lot here that I’d like to talk about. First of all, they are spell casters and have some pretty solid spells to choose from in a pinch. The spell save DC of 13 is a bit low in my opinion, but thankfully only 2 of these spells use it.
Darkness and Invisibility can be used offensively or defensively to help the oni control the battlefield and try to hinder their enemy’s ability to work together. Charm Person is another excellent choice in terms of lore and flavor for oni.
Gaseous Form can be used in a pinch to escape from the battle, or simply as a mid-combat repositioning tool. Sleep is a bit riskier as it only affects 5d8 hit points worth of creatures, but if it’s gotten its enemies weak from its Cone of Cold it could be a great way to give it automatic critical hits on sleeping targets.
Magic Weapons seems like more of a flavor choice than anything else. There’s very little that gives PCs resistance to non-magical slashing damage, but it’s nice if its able to overcome this resistance.
Regeneration is particularly powerful. While other creatures like trolls and vampires have Regeneration it’s not nearly as effective since their regenerative abilities are reliant on not taking certain types of damage the previous round. Oni’s regeneration cannot be stopped as long as it has 1 hit point.
Multiattack. The oni makes two attacks, either with its claws or its glaive.
Claw (Oni Form Only). Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 8 (1d8 + 4) slashing damage.
Glaive. Melee Weapon Attack: +7 to hit, reach 10 ft., one target. Hit: 15 (2d10 +4) slashing damage, or 9 (1d10 + 4) slashing damage in Small or Medium form.
Change Shape. The oni magically polymorphs into a Small or Medium humanoid, into a Large giant, or back into its true form. Other than its size, its statistics are the same in each form. The only equipment that is transformed is its glaive, which shrinks so that it can be wielded in humanoid form. If the oni dies, it reverts to its true form, and its glaive reverts to its normal size.
Honestly, there’s not much to write home about here. Change Shape will probably not be used unless the oni is caught by surprise by the party while it’s in a smaller form. Realistically the oni would avoid fighting outside its true form at all costs using its spells to buy it enough time to get away or change into its true form.
Its glaive attack is on-par with large creatures plus it has a bit of reach which is great when paired with the oni’s flying speed. I can’t see a use for its claw attacks as it also deals slashing damage and doesn’t benefit from reach.
Damage Avoidance and Maneuverability
You can’t hit what you can’t see and oni live by this motto by having the ability to cast invisibility and darkness at will. Gaseous Form and Sleep also help with an oni’s ability to impede on its enemy’s ability to damage them.
The combination of 30 ft. fly speed and a 10 ft. reach melee weapon is still extremely powerful. This combination makes the oni extremely difficult to hit for melee characters.
Having reach is a huge advantage on the battlefield even when 3-D combat isn’t a factor. Reach allows you to reposition yourself without provoking attacks of opportunity, while your opponent is not able to do the same without using an Action to Disengage.
Change Shape deserves a quick mention here as well. If the oni is in a situation where it could blend itself into a crowd of people this ability becomes yet another way for the oni to escape and reposition.
Regeneration and Reengaging
The oni’s superb ability at avoiding damage and escaping from an unfavorable fight is just one way the oni has at being a solid defensive creature. Tack all this onto a creature with 16 AC and 110 HP and you have a steel wall of flesh that can fly.
Its ability to escape with its spells is huge and not for the reason you may be thinking. Sure an oni can escape a near-brush with death so that it can plot and exact its revenge on the party for another day.
However, an oni’s Regeneration allows it to regenerate its entire health pool in just 11 rounds of combat. That’s just over 1 minute of in-game time. Invisibility lasts an entire hour and Gaseous Form both last up to an hour giving an oni ample time to regenerate its hit points.
While the oni can regenerate its hp rapidly, the party cannot. If the party is unable to finish the oni while it is invisible and on the run, it can easily ambush the party again as they attempt to recoup from their initial run-in with the oni.
A Powerhouse of Damage
I typically limit the Strengths and Weaknesses sections to 2 of each, but oni are very powerful creatures that I just had to add a 3rd to the list!
If we assume Cone of Cold is going to hit an average amount of damage (36) against a party of 4 it’s going to deal a whopping 144 cold damage in a single burst. Despite this, it’s going to be guaranteed damage to some degree as rogues and monks cannot use their Evasion to avoid a Constitution Saving Throw.
Oni only have one cast of Cone of Cold as their ranged option in combat. It’s nothing to scoff at, but it’s definitely a surprising weakness for a creature that excels offensively.
The 10 ft. reach of the oni’s glaive with flying speed is phenomenal in general. However, against a party filled with a lot of ranged attackers, the reach doesn’t do a ton.
For example, Ray of Frost can pepper the oni from up to 120 ft. away and slow it down. These types of abilities that hinder the oni’s ability to position are the bane of its existence as it has practically no option to retaliate against its enemy.
Oni need to rush at their opponents than try to reposition in melee to have a fighting chance.
The oni’s lack of ranged options needs to be supplemented by ensuring that the party cannot kite the oni to death. A small room or confined space is where the oni is going to thrive. They need to guarantee that their one ranged AoE ability is going to deal a worthwhile amount of damage.
How to Play an Oni
Maximize Your Damage Potential
You should only use Cone of Cold when you can guarantee that you can hit the majority of your enemies. Cone of Cold is a fantastic opening ability in the right circumstances.
Sleep allows you to put 5d8 (22.5) hp worth of creatures to sleep on average. Using this after a successful cast of Cone of Cold could allow you to CC one or more enemies.
If you happen to pull of this combo be sure to remember that attacks on sleeping creatures are at advantage for melee attacks and deal automatic critical hits if you are within 5 ft. of the creature. You may have to temporarily go out of position to do this, but it’s well worth it to forgo your glaive’s reach to get a free critical hit.
Another option is to use invisibility to make you an unseen attacker. This will grant you advantage on your first hit on a target that cannot see you. This can be useful for securing a take-down on a creature that is at low hp.
Besides these specific maneuvers, simply make use of your flying speed and position yourself above melee creatures. You should be able to hit them while they’re helplessly trying to jump in full plate armor and unable to reach you. 30 damage per round with your glaive isn’t anything to scoff at.
Make Use of Your Exceptional Positioning
Make any front-line enemy that doesn’t have a ranged option regret their decision. Float above the tanky front-line characters’ heads and pinpoint the casters and low AC enemies.
Darkness and Sleep can be used to knock out casters or keep them out of the fight for a round or two while you deal with the tankier characters.
Use Gaseous Form or Invisibility to position yourself safely away from the party without provoking opportunity attacks, or simply get into confined spaces that the party cannot follow.
Anything you can use to avoid as much damage as possible while you regain 10 hp per round is going to be considered a win.
Oni have seen a lot of love as of late in Critical Role and in one of my favorite adventures in Tales from the Yawning Portal, Escape from White Plume Mountain. In both are manipulative, ruthless villains that take advantage of tight-quarters encounters to deal a large amount of damage to the unsuspecting heroes.
I feel that oni are more powerful than their CR gives them credit for. It was genuinely difficult to come up with weaknesses for them as a creature which is why I opted for 3 strengths 1 weakness instead of the usual 2-2 split.
They do lack damage resistances and immunities, but with flying speed and unhindered HP regeneration they’re not missing out on much. I’d say that their defenses are on-par with CR 7 if not slightly above it.
The damage that they’re able to pull off in the first 3 rounds of combat is impressive. Plus this assumes that no one triggers attacks of opportunities from the oni with its extended reach.