How does summon greater demon work 5e d&d?

Summon Greater Demon 5e includes the following line: The demon vanishes when it reaches 0 hit points, or when the spell ends.“. You can end your focus on a spell at any moment. It doesn’t need to be taken. You can end the spell at any moment, and the demon will disappear. It is a spell from Xanathar’s Guide To Everything

Conjuration
Level:4

Casting time1 Action
The range60 feet
Components: V, S, and M (a vial containing blood from a humanoid that was killed in the last 24 hours)

Duration: Concentration for up to one hour

You curse, summoning one demon out of chaos in the Abyss. You select the type of demon you wish to summon. It must have a challenge rating less than 5, such as a shadow or barlgura. The demon will appear in an unoccupied space that you can see within its range. It will disappear when it drops below 0 hit points or when the spell ends.

Roll initiative to summon the demon. It has its turns. You can summon the demon and issue a verbal order to it on each of your subsequent turns. It requires no action from you. It will then tell you what it should do next. It will attack any creature that is within its reach if you don’t issue a command.

Each demon makes a Charisma saving throw at the end of its turn. If you speak the demon’s true name, it has a disadvantage on this saving throw. The demon will continue to obey you even if your save fails. Your control over the demon is ended after a successful save. The demon will spend its turn pursuing non-demons and attacking them to the best of its ability. Uncontrolled demons can’t be stopped concentrating for more than 1d6 rounds if they still have hit points.

You can create a circle with the blood as a component of the spell by casting it. You can make the circle large enough to cover your entire space. The spell is good for a while, but the summoned demon cannot cross it or harm it. It can also not target anyone within the circle. The spell’s end can be broken by using the material component.

The demon vanishes 1d6 rounds after the spell ends. You can stop focusing on the spell, and the demon will come back from where it came from.

Suppose the demon does not have a plane shift or teleport ability. In that case, it will not return home unless it has access to a nearby portal.

At higher level

Cast this spell with a spell slot at the 5th or higher level. The challenge rating goes up to 1 for every slot level above 4.

Page: 166 from Xanathar’s Guide To Everything

Do you want to summon a demon?

Demons are a specific type of creature. It even lets you limit them by CR so that you can get lists like all demons of CR 5 or lower. These lists will contain certain variants, such as the summoner demon and the reduced threat monster variants. The GM can decide whether any of these variants are possible to summon.

Particularly, “demon”, a Monster tag, is briefly covered in the Monster Manual page 7.

One or more tags might be added to a monster’s type in parentheses. An example of this is the humanoid (orcs) type for an orc. Parenthetical tags can further categorise certain creatures. Although the tags do not have any rules, they can be referred to as games or magic items. A spear that is particularly effective in fighting demons could be used against any monster with the demon tag.

If a monster is a demon, the demon tag will appear in their statblock; for example, the quasit has a statblock that contains the following at the top:

Tiny fiend, demon, shapechanger, chaotic evil

It means it is a fiend but also a demon. It is also a shapechanger for any features that depend on these terms, such as the summon greater spell.

Can you twin summon greater demon in 5e dnd?

No. To twin a spell, it must be a spell that “targets only one creature and does not have a range of self” while 5e summon greater demon “appears in an uninhabited space you can see within range.

Summary

Here are a few important points for Summon Greater Demon 5e:

The demon is independent and takes its own decisions. It will attack any creature it sees, even if you don’t give it a command. It attacks all non-demons if it is free.

As illustrated by its charisma saving throw, the demon actively attempts to escape your control.
As part of summoning, you will create a magic circle to protect you from demon attacks.
The demon can be summoned again for 1d6 rounds if you stop concentration.

A demon is naturally motivated to kill. It does not care about who it kills, but it does not want its kind to die. It means that the demon is affected by your influence and blinded or otherwise unable to discriminate between different targets.
Controlling the demon is not something it likes. You are unlikely to control the demon, and it will not like you.
The assumption is that a demon can at least turn against you. It implies that it has happened to someone in the past. That’s why the spell includes a safeguard.

The demon can be very powerful and can use the rift you create (or any other mechanism to get them here) to stay longer.

I would still recommend that the details be left to the DM. You can make a lore-based exception, and I don’t see anything wrong with it, especially if the rules mechanic-wise are not changed. A friendly demon, for example, might not like being summoned in this manner and should be controlled within the first minute. It also goes blind rage if there is a fight. The demon is generally friendly. While this does not affect the battle, it does make it easier to play roleplay and avoid combat. However, I believe that balancing is necessary for combat situations. It can be tricky when combat and RP mix. However, I believe it is okay for the DM not to have too many rules. If they feel comfortable, they can always restore balance if necessary. If everyone thinks it is great and the DM is having fun, you can’t go wrong with summon greater demon 5e.