- "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]
After this spell was performed, Buffy possessed enhanced Slayer powers, Willow's magic, Giles' knowledge of foreign languages, and Xander's strength. Her eyes and voice were altered as well.
- "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 respective talents into one (Willow wanted to cast a spell on Adam, but only Giles knew how to pronounce the spell's wording correctly) causing Giles to remember that such a ritual existed. The spell required the use of cards, candles and a mystical gourd.
- "The power of the Slayer and all who wield it.
Last to ancient first, we invoke thee.
Grant us thy domain and primal strength.
Accept us and the power we possess.
Make us mind and heart and spirit enjoined.
Let the hand encompass us. Do thy will.
By the generous will of the Ancients, the almighty power of the Divine Spirits…
Your supplicants humbly beseech thee to behold us, and that which we possess…
the moieties of the One, the Avatar…
And Manus... the hand.
We enjoin that we may inhabit the vessel, the hand...
daughter of Sineya...
first of the ones...
We implore thee: Admit us
bring us to the vessel !
Take us now !
We are heart...
We are mind...
We are spirit...
From the raging storm...
We bring the power of the Primeval One..."
- ―The enjoining spell[src]
After Buffy's essence became one with those of her friends' through the spell, she gained the powers of:
- Spell Casting: Buffy had the ability to cast powerful magical spells, which she used to negate Adam's attacks and ultimately destroy his radioactive uranium power core. Examples of other abilities she derived from this power are:
- Force-field Generation: Through a Sumerian spell, Buffy was able to access the ability of projecting a powerful field of manipulated energy - conjuring a barrier to block Adam's bullets.
- Transmogrification: Through another Sumerian spell, Buffy was able to access the ability of transforming objects - she transformed one of Adam's rockets into three doves.
- Technology Manipulation: Buffy was shown to possess the ability of manipulating electronics and machinery - with a wave of her hand, she caused Adam's weapon arm to morph back into a regular demon arm.
- Enhanced Slayer Attributes: Buffy's Slayer strength, speed, and reflexes were dramatically enhanced, enabling her to best Adam in a physical fight and ultimately back him into a corner. She was even able to literally rip out his power core, killing him.
- Levitation: Buffy had the ability to make objects fly into the air, as seen by how she made Adam's power core hover into the air before destroying it.
- Banishing/Vanishing (possibly): Given the method that Buffy used to destroy Adam's power core (immersed in white light and vanishing), it was possible that she had the ability to either banish or make objects disappear into thin air.
- Sumerian: Buffy was fluent in Sumerian - all of the magic spells she employed in her fight against Adam were shown to be spoken through this language.
It is unknown if Buffy was able to access other supernatural powers when she was in this empowered state, given how she gained seemingly omnipotent control over magical forces. However, it was reasonable and logical to deduce that, while Buffy was in this state:
- Her magical abilities came from her drawing upon Willow's witchcraft powers.
- Her fluency in Sumerian came from her drawing upon Giles' knowledge of languages.
- Her knowledge of spells came from Willow's and Giles' combined knowledge of magic.
- Her enhanced Slayer powers came from the combination of her own abilities, Xander's physical strength, and Sineya's very own powers.
In this empowered state, when Buffy spoke, so would Willow, Xander, and Giles. When Buffy managed to destroy Adam's power core, the spell faded abruptly, leaving her and her friends drained of strength.
- 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.