Pet Lich

The Demon Faction's Warp Portal into the Buried City was actually upon a colossal stone platform rising out of the ground.

The Underearth people used remarkable underground construction techniques to secret away another group of Demigod-tier Guardians beneath the Buried City: Ten champions standing guard over the criminals of the Underearth people, taking advantage of the cramped quarters within the tunnels to hold their position within that hidden underground world for centuries.

Once the Demon Faction had helped to locate the ten Crystal Orbs, the Warp Portal that had been hidden within the earth was activated, linking it to all the towns of the Demon Faction.

It was very similar to the Angel Faction's own circumstances: The Demon Faction's Warp Portal was guarded by Demigod-tier NPC champions; although the Spire of Hades did not extend into the Warp Portal, players who had attained Tier 5 were allowed through.