Valhalla Gate

Valhalla Gate and Valhalla Gate Another are two of the most powerful spells in the series as they can kill absolutely anyone, for a great price however

Appearance
It consists of two parts, the first being the actual gate itself, and the other is the sentient statue placed on top of it.

The gate itself appears to be styled after a 'hellish gate' of the sort, having spikes all over it, and an over devilish look.

Atop the gate is a sentient stone statue (a female angel in the anime). It is primarily grey with white eyes, lacking pupils, and can cry blood. The statue is always seen smiling. Off notice, while the gate can only open and close, the statue can freely move its arms

Personality
While the gate itself lacks personality the statue does have a personality. It is constantly laughing. It is also very aware of how strong it is, reassuring Mash that the Demon Lord is in the void and will not return. It also takes joy in the fact that whoever cast it will die, laughing at Seiya for it. Despite this, it claims to be fair, as it always takes the 'toll' at the same cost (namely, the casters life), calling itself a servant of the underworld.

Powers and Abilities
Since it can kill anyone, regardless of how strong they are, it is one of the most powerful beings in the series. Whereas the Demon Lord was capable of escaping the original Valhalla Gate it was not capable of escaping Valhalla Gate Another (because that Valhalla Gate Another swallowed the original Valhalla Gate as well). However when summoned it will also kill the caster. Valhalla Gate Another also mentions that while you can escape the death of the original Valhalla Gate, no one can escape the death of Another. It is not known if Valhalla Gate Another actually kills his enemies or simply traps them. The statue mentions that 'the Demon Lord is in the Void and will never escape', thus making it a bit vague whether he actually kills or not.

Users
Valkyrie knows how to use the spell and even delights in the pain it inflicts on her in the aftermath. She later teaches it to Seiya.

Trivia

 * When Valkyrie uses the Valhalla Gate, her HP goes from 999,999,999 down to 319,851 implying that it consumes 999,680,148 HP from its caster. This proves the fact that no human being will survive the recoil as the highest HP from a human being that was shown was from Ethan Sifford with 587,654 HP.
 * It was shown that Ristarte was able to heal Seiya from Valhalla Gates recoil by using Order. This implies that Ristarte can restore more than 999,680,148 HP when using order.