The fearsome Oni comes to the D&D 5e Monster Manual straight from Japanese mythology.

Also known as “Ogre Mages,” these hulking creatures have a never-ending hunger and a particular taste for human children. Whispered voices and legends passed down for generations warn children against going out at night for fear of the Oni. These creatures have become the boogeyman that haunts the nightmares of adults and children alike.

In stalking their prey, the Oni uses its shapeshifting magic to blend in with the people it is terrorizing. When the time is right, the Oni reveals its true form and strikes with either its claws or massive glaive.

In pursuing their evil goals, the Oni is cold, calculating, and ruthless.

Today we are taking a closer look at the Oni in D&D 5e!

Physical Appearance of Oni in D&D 5e

It is difficult to say what stands out as the most terrifying aspect of an Oni’s physical appearance.

As distant relatives of Ogres, they have large, hulking bodies and stand over most humanoids. Their skin is a deep blue or sickly green that add to the Oni’s demonic appearance. Long, black claws extend like daggers from each of the Oni’s fingers.

Dark and matted hair hangs low from their head and only draws more attention to the ivory horns on the Oni’s forehead.

But if only one thing could be chosen as what is the most terrifying part of the Oni’s appearance, it might have to be their face.

Their large eyes are dark as night with pupils that are strikingly white in contrast. With their signature smile, the Oni’s large mouth reveals dark and jagged teeth and the stench of death.

Ogre Mages

Oni possess a natural magical ability. As they look for ways to enhance this, they might be drawn to working with other evil entities who could provide such benefits. After all, who doesn’t love a lucrative arrangement? To this end, magical items are commonly used by evil wizards or hags to gain the service of an Oni. Though the Oni’s love of luxurious items and wealth mean that magical items are likely only part of the deal.

The Oni’s magic primarily focuses on its ability to stalk and ensnare victims. Spells such as Invisibility, Charm Person, and Sleep aid the Oni in rendering its victims helpless. If forced to fight, the Oni will not hesitate to use its Cone of Cold to dangerous effect.

Oh, and did I mention that they can fly?

Yeah… They do that too…


An Oni can be remarkably difficult to track down. Using magic, these creatures are able to change their form to conceal both their shape and size.

During the day, the Oni uses its shapeshifting ability to blend in with the residents of a town or village. Commonly, they’ll disguise themselves as travelers or frontier folk.

A disguised Oni might very well volunteer help with manual labor to further gain the trust of the townspeople. They seek to appear as harmless newcomers while all surveying to identify particularly tempting victims. When such a potential victim is identified, the Oni begins devising plans to lead them away and devour them.

Oni in D&D 5e – Combat and Tactics

The Oni in D&D 5e is a combat powerhouse. Despite being a CR 7, Oni seem to hit stronger than others at the same Challenge Rating. With powerful magic and ferocious swings from its glaive, the Oni can put out a large amount of damage in a short amount of time.

Underestimating an Oni can very quickly become the last thing that a party ever does.

When discussing the Oni in combat, I think it’s best to break it down since there are so many ways the Oni can fight.

The Oni’s Glaive

The Oni has multiattack which means that it can make two swings with its glaive. If fighting in its true form, each of these swings does 2d10 + 4 damage if they hit. The Oni’s brute strength is definitely something to watch out for.

Keep in mind that the glaive has reach which means that the Oni can dish out some nasty attacks of opportunity when an enemy leaves a 10ft range. Furthermore, an Oni can fly 10 feet over an enemy and attack while being safe from most melee attacks.


An Oni can quickly dominate a battlefield thanks to its ability to fly and some nifty magic abilities. By going invisible at will, the Oni can then fly to an undefended enemy and surprise them on its next attack with advantage for being invisible.

Cone of Cold

This is the big one.

Cone of Cold is a very powerful spell and can potentially be a TPK if used right. It’s unlikely that the Oni will open with this ability, but if its enemies are in a perfect formation it might be tempted to do so.

Generally, the Oni will use its Cone of Cold if the party is putting up a better fight than it anticipated. This gives the Oni an opportunity to dish out some crazy damage and even the playing field.


Each round that the Oni has at least 1 hit point left, it regenerates 10 hp. Unlike Trolls, for example, whose regeneration can be stopped if they take fire or acid damage, this regeneration just constantly goes.

If an Oni is particularly wounded, it may choose to go invisible and fly to safety to regenerate. Depending on how the party is looking and whether or not the Oni believes it can finish them off, it may reengage after a round or two.

Regardless, the only way to kill an Oni in D&D 5e is to make sure that you deal enough damage to stop its regeneration. Otherwise, it can be back in no time at all.

Choosing Targets

Despite their brutish appearance, Oni are not the classic “big, dumb, and scary” monster. They are intelligent enough to be tactical in combat.

An Oni will initially look for a party member that it believes it can drop quickly. It may attack this character with its glaive or (if they’re ranged) by casting darkness on them so that they have to move closer into combat.

However, if one character is particularly doing a lot of damage to it, the Oni will concentrate its efforts to remove that threat. After that, the Oni can resume picking off the weaker party members.

This is especially important if the Oni decides to be trickier and use its invisibility to surprise enemies. It will want to focus on whoever seems to be at the lowest HP or is most isolated from the rest of the group.


By the time the party is able to face an Oni, the Sleep spell is not a solid choice for an opening spell.

However, it can be useful after combat has gone on for a few rounds or following a Cone of Cold. By putting the weakened enemies to sleep, the Oni can focus its attention on whoever is still standing.

An Oni is cruel and always hungry. It will have no reservations about finishing off a sleeping enemy to devour once combat has finished.


As mentioned, the Oni’s ability to cast invisibility at will is a particularly dangerous attribute. This should absolutely be used by the Oni to create as much fear as possible in the party. As they group together to better defend against their unseen enemy, the Oni may see this as a prime opportunity to unleash its Cone of Cold.

If the combat is going poorly, however, Invisibility and its ability to fly give the Oni a way to quickly escape.

Gaseous Form

Gaseous form is not a spell that the Oni should use as an escape plan. Its movement is reduced to 10ft per round and the spell requires concentration.

What Gaseous Form IS good for, however, is buying extra time for the Oni’s regeneration ability if necessary. For example, if the characters are able to see through the Oni’s invisibility, this is a good back-up plan for avoiding further damage while regenerating.

Additionally, if the party tries to run away from the Oni, gaseous form gives it a method of chasing them down. Seeking shelter in an abandoned shed, for instance, may be a good tactic until the Oni is able to creep in through a small hole with its Gaseous Form.

Roleplaying an Oni in D&D 5e

The Oni’s intelligence and evil nature should be prominently featured when roleplaying an Oni.

Disguised as someone else, they can gain the party’s trust. Only when the time is right will the Oni strike at the party members.

Have it mock and taunt them for falling for its ruse. The Oni wants to see the fear in its victim’s eyes before it goes in for the final blow.

Using an Oni in Your Game

Oni make for incredible boss encounters at low-mid level play. By the time the party is around 5th level, they may be unwittingly playing into an Oni’s schemes.

The Oni could be disguising itself as a quickly beloved NPC and may even aid the party on some occasions to further its own ends.

Conversely, the Oni may be using its disguise to downplay how threatening it is. What may appear to simply be the leader of a group of bandits could actually be an Oni in disguise!

For some further inspiration in how to use an Oni in your game, you may check out season 2 of Critical Role (no spoilers) or the White Plume Mountain adventure in the fantastic Tales From the Yawning Portal book.

Of course, it’s possible that Oni is also working for an even bigger villain who has retained the services of the Oni. It’s possible that the campaign’s BBEG hasn’t taken any particular notice of the party until they defeat his Oni lieutenant.

Conclusion – Oni in D&D 5e

So clearly there’s a lot to be said about the Oni in D&D 5e.

Few monsters have the potential in both combat and roleplaying that the Oni has. If used correctly, the Oni can be one of the most memorable encounters that your players will ever have in playing D&D. Though whether these encounters are good memories or terrifying nightmares is up to their characters and dice.