Sounds interesting with a ladder system.
What part of the normal game will the Arena feature? Will you start with a hero and a city? An army of 5 units + hero? Specific starting conditions relating to cities, spells, items, hero and unit?
For example the Arena-mode will you start with one hero (choosable), 2 archers, 2 riders and 100 mana, a random selection of 3 common tactical, 2 uncommon strategic and 1 rare tactical.
Vision: A world free of SK;
Objective: Find and destroy the SK and SK units, SK Fortress (a cool name is needed for the SK fortress aka. Barad-durM;
Tactical goal: Apply the relevant spells to give some b-hurt to a wannabe Raistlin
edit: The Direshop sounds really interesting. Would love to hear more about how you can spend doomsday points. Does "spend" mean the doomsday counter goes up? So for example you can sell your soul to the SK (aka devil) and get a fabulous fantastic item to slay the SK.