Acheron, Debenter, Uruk & Nars

Acheron arrived with the eX700 expansion, in the same update that added the guild war Arca War and the Elemental System with its five elements: Water, Fire, Wind, Earth and Darkness. Almost everything that lives in Acheron and its later regions is an elemental monster.

To get in, collect 5 Spirit Map Fragments to make a Spirit Map, then hand it to Captain Slough in Noria. The fan wiki lists these monsters in Acheron: Devil Fairy, Elemental Beast, Elemental Knight, their Ubaid versions, Gnome, Hellraiser, Salamander, Sylphid and Undine.

Webzen introduced Debenter in Season 8 as the Darkness Valley, a part of Acheron where Kundun, the God of Darkness, calls up his monsters. It was described as darker and creepier than earlier areas, with new monster types.

Debenter and Uruk Mountain are where normal Bloodangel mastery armor drops, for characters past their 3rd class change and over level 400.

• Uruk Mountain (spelled Urk Mountain in the Season 9 guide) is a hunting ground inside Acheron with tougher monsters.
• Enter through the portal at (66, 221) in the Acheron safe zone.
• Arca War and Protector of Archeron are not held here. If you die or log out, you return to the Acheron safe zone.
• Killing Lord Silvester drops 3 special rewards chosen from: a Pentagram, a socket item, a sphere or a tetra crystal.

Nars, described by Webzen as the 5th region of Acheron, has normal elemental monsters plus a separate boss area. You reach it through the Nars Entrance gate at (90, 182) in the Acheron safe zone. Inside, the Red Gate links (179, 185) with (127, 34) and the Blue Gate links (179, 210) with (37, 195). Dying or leaving the game sends you back to the Acheron safe zone, and Arca War does not run here.

Core Magriffy respawns every 24 hours with a random element (Fire, Water, Wind, Darkness or Earth). Its skills: Poison on basic hits, Twister (four whirlwinds that pull targets in), Shout (area damage with knockback), Clone (a fake copy; hitting the wrong one enrages it), Berserker (+100 damage per use, stacking) and Life Regeneration when no one is near. It drops 4 items, among them Pentagrams and the mountable Muuns Repen, Pawn and Grippus. Excellent Bloodangel mastery gear also drops only in Nars.