Is there any way for a wizard to summon a Celestial or Fey for Planar Binding?

Question

Planar Binding allows a wizard to attempt to bind a celestial, elemental, fey or fiend to one’s service. Only clerics seem to have the spell Conjure Celestial and Druids or Warlocks have Conjure Fey. Wizards appear to only have Summon Lesser Demons, Summon Greater Demon or Conjure Elemental.

Planar binding states:

With this spell, you attempt to bind a celestial, an elemental, a fey, or a fiend to your service. The creature must be within range for the entire casting of the spell. (Typically, the creature is first summoned into the center of an inverted magic circle in order to keep it trapped while this spell is cast.)

If a wizard wants something other than a demon or elemental in their service such as having a high level lawful good Fey or a Celestial like a Ki-rin - what way could they possibly conjure one that could be kept in a magic circle long enough to use Planar Binding?

Answer 1

Spellcasting Services

Hiring a level 13 druid to cast a spell is relatively cheap through the spell druids use only summon a CR 6 fey creature. While on the other hand a celestial conjured by a cleric has CR 4 rating at most so unless you plan to rely on mob tactics they might not be a good choice for you.

Using Plane Shift

You don't need to summon a fey or a celestial creature to the world in order to bind them. You can use plane shift in order to get to feywilds or heavens in order to find yourself a strong angel/fey before beating them till they are unconscious and putting them in a magic circle. Also ironically you don't have to bind someone to the plane you intend to use them in.

Gate

If you know of a strong creatures name you can use Gate to drag them to your realm before attempting to bind them through doing so may require a high intellect roll.

True Polymorph

You don't have to bother finding a fey or celestial at all. According to the description of True Polymorph

Creature into Creature. If you turn a creature into another kind of creature, the new form can be any kind you choose whose challenge rating is equal to or less than the target's (or its level, if the target doesn't have a challenge rating). The target's game statistics, including mental ability scores, are replaced by the statistics of the new form.

Basically find yourself something you can summon and then use true polymorph on them turning them into a fey or a celestial creature before using binding or them. Or you can bind them first and then transform them into a fey or celestial creature.

Use Wish

I know it is a really cheesy answer but cheesy answers work sometime. You can wish to summon a powerful celestial or fey creature to the mortal realm through chances are your DM will require you to defeat the creature first before binding it.

Answer 2

Frame challenge: summon lesser demons and summon greater demon won't work either.

If you are looking for a way for the same wizard to cast planar binding on a creature that it has conjured or summoned, it may be harder than you think. A spell that conjures or summons a creature typically requires concentration. Conjure elemental, summon lesser demons, summon greater demon, conjure celestial and conjure fey all do.

For most of these spells, one spellcaster would have to cast the spell to conjure or summon the creature, and maintain concentration on it while a second spellcaster casts planar binding. This is because planar binding has a casting time of 1 hour, and when a spell has a casting time of longer than 1 action, the caster has to use concentration throughout the casting (Player's Handbook p. 202), so they cannot concentrate on another spell at the same time.

Even if conjure celestial were on the wizard spell list, you would run into this issue. You also run into this issue with the new summoning spells from Tasha's Cauldron of Everything.

However, this could work with conjure elemental.

A wizard can cast conjure elemental, trap it inside a 4th-level or higher magic circle that had previously been cast, drop concentration, and the elemental won't disappear for an hour. The wizard can then immediately cast planar binding on it. (A 3rd-level magic circle would likely disappear before the planar binding casting was complete.)

This would also work for conjure fey if it were on the wizard spell list.