Abyss Altar

In version 2.0, the invasion of the dark forces happened because of the proliferation of anti-Human warlocks, mages and sorcerers in the legendary continent.

They fell to the dark side and constructed the Abyss Altar in the Devil’s Den. They sacrificed live creatures to the darkness in exchange for dark powers.

However, the Abyss Altar, it was a big deal. At least one anti-human NPC guarded such an cave

The more powerful the NPC was, the lesser were the numbers of creatures required to guard the cave.