The Seal of Danzalthar was a mystical seal located at the Hellmouth. It served as the entrance to a massive cavernous area in which thousands of Turok-Han vampires awaited to be unleashed. Its design resembles a goat with its tongue out, a theme which can be found in various recurring locations as it is a common symbol of the Devil or of Satanic worship. It opened only when a large quantity of blood was spilled on it and closed when the blood stopped flowing. However, while closed, it still remained active, emitting a constant flow of unholy, corrupting energy which only stopped when bathed in tears of repent by the one who "opened" it.

Openings and Attempted Openings

• The First (as Warren Mears) convinced Andrew Wells to stab Jonathan Levinson on the seal. However, Jonathan didn't have enough blood to open it because of being anemic.
• The First (as Warren) used Andrew again to try and kill a pig to open the seal, but the pig got away.
• Andrew was going to try again using pig's blood from a butcher's shop, but got intercepted by Willow.
• The First strung up Spike above the seal and cut his chest, using his blood to open the seal releasing the first Turok-Han.
• A demon girl that Xander was on a date with kidnapped him and strung him up above the seal in the same way that Spike was; the seal began to open, but was stopped before any Turok-Han could emerge.
• The Slayers Buffy and Faith, along with the Potential Slayers, used blood from their hands to open the seal to go in for the final battle.