I have come up with an idea for the last world (which will, more likely than not, be Umbra).
Storyline Morganthe is finally getting ready to darken the Spiral using the "Orb of Umbrification", a mystical orb that, when charged, turns any and all of the Spiral's worlds dark and... well... Umbra.
First, she goes to the Fire School and steals the "Book of all Things Fire Magic". She combines her new Fire knowledge with the Death school she already was, and mixes Umbra culture into that, to make the Umbra School (an enemy only school).
She then goes to the world of Umbra, where she begins to enchant everything there with Fire magic, to make Umbra magic. You need to find the seven Resistance Leaders: Mr. Dissipate, Mr. Vaporize, Mrs. Entangle, Mr. Unbalance, Mrs. Melt, Mr. Strangle, and Mrs. Quench. Together, they can weaken Morganthe enough for you to duel (and possibly defeat) Morganthe for good.
When you get to her tower, she is charging up the Orb of Umbrification. She sends out the Umbra King Memoso to stall while she finishes the ritual, then duels you to stop you from taking out the orb. When the player(s) win, they stop the orb and nullify the corruption in Zafaria, MooShu, and Krokotopia. Congratulations, you just completed the second story arc!
Areas Upper Nexus: This place has been taken over by the Fire enchantments, and there are strange crystals around the area. Only Mr. Dissipate has resisted the enchantments. There is a broken portal to the Lower Nexus.
Ether: Morganthe created this between the Upper and Lower Nexus. Several magical forcefields block your passage to the Lower Nexus. The spiders here might have something to do with the forcefields....
Lower Nexus: This place has also been corrupted by Morganthe. Only Mr. Vaporize survived, and monsters run rampant. There are three portals around the Lower Nexus to other areas (don't have names yet).
