- “So no problem, all we need is combo Buffy; her with Slayer strength, Giles' multi-lingual know how, and Willow's witchy power.”
- ―Xander Harris[src]
The enjoining spell is a ritual which calls upon the spirit of the First Slayer to combine the essences and abilities of several individuals into one super-powered being.
- “The enjoining spell is extremely touchy. It's, uh, volatile. We-we can't risk it being interrupted.”
- ―Giles describes the dangers of the spell.[src]
The core four members of the Scooby Gang—Buffy Summers, Xander Harris, Willow Rosenberg, and Rupert Giles—performed the spell in 2000 to defeat the bio-mechanical demonoid Adam. Xander unwittingly inspired the use of the spell by suggesting that they needed to combine their powers into one, causing Giles to remember that such a ritual existed.
- “The power of the Slayer and all you yield it.
Last to ancient first, we invoke thee.
Grant us thy domain and primal strength.
Accept us in the power we possess.
Make us mind and heart and spirit joy.
Let the hand encompass us. Do thy will.
And Manus... the hand.
We enjoin that we may inhabit the vessel, the hand...
daughter of Sineya...
first of the ones...”
- ―The enjoining spell[src]
The four performed the spell in the underground Initiative facility. Willow acted as the spirit, Xander as the heart, Giles as the mind, and Buffy as the hand. This caused Buffy to become a seemingly omnipotent being possessing enhanced strength and speed, as well as magical abilties like telekinesis and transmogrification. After a brief fight, Buffy ripped out Adam's radioactive uranium power core, killing him. Her abilities faded immediately afterwards.
- Giles: “Somehow our joining with Buffy and invoking the essence of the, the Slayer's power was an affront to the source of that power.”
- Buffy: “You know, you could have brought that up to us before we did it.”
- — Giles explains the consequences of the spell.[src]
The enjoining spell had notable after effects. A Slayer calling on her friends to aid her in battle offended the spirit of the First Slayer, who believed that the Slayer should work alone with no connection to humanity. She proceeded to invade the dreams of the Scooby Gang, killing them one by one to punish them. Buffy eventually put a stop to her by simply rejecting what she had to say and waking up.
Despite her rejection of the First Slayer, Buffy became more accepting of her role as the Slayer and began to willingly study her power and history.