I plan to have a series of quests rather than just one single big quest. Generating quests/content is one of the most time-consuming aspects, so doing a series of shorter quests helps breaks the task down. Currently there are three quests, but more will be added in time. Version 0.6 also introduces the ability to play a randomly generated dungeon.
It shares some ideas with roguelikes (randomly generated levels, option for permanent death, optional keyboard controls, and of course the whole idea of a single player hack-n-slash dungeon crawl), however I didn't want to restrict the game to an axis-aligned tile-based world, or to being turn-based. Passageways/rooms are defined as convex polygons, and scenery can be any size or location. Quests are defined in external XML files.
I'm using Qt to develop Erebus. This is the official API for Symbian which I wanted to support (after seeing the potential for lots of downloads on my other apps like Wifi Remote Play), but also allows easy support for many other platforms including Windows, Linux and Android (via necessitas). Whilst usually thought of as a GUI API, Qt is a complete application framework, providing all of the low level APIs useful for games like windowing/input/networking that you'd get in libraries like SDL, as well as higher level support for 2D graphics. I ended up using it for the UI too, which greatly simplified development.
Erebus is Open Source, released under the GPL v3 or later. Almost all of the game art comes from 3rd party Free sources (with particular help from Open Game Art and Flare.)
Older versions have been reviewed - v0.5 at Free Gamer, and v0.3 for Symbian on All About Symbian. It's always a bit nerve-wracking for me to see someone writing about my work, but the coverage is good, and any constructive criticism helps improve the game.
The Symbian downloads have now passed 57,000, with mostly 5/5 reviews, and an average rating of 4/5 (to the nearest integer - Nokia Store doesn't show the fraction). (It was also an interesting lesson to me to not get too down from random negative ratings - after an inital 5/5, the next two in a row were 1/5 with comments like "boring", leaving me rather depressed - thankfully the response after that has been different!)
Also see the main Erebus blog.