It's a worker-placement game like Caylus or Pillars of the Earth: each round, you get to place your meeples to collect resources and take different actions, but only one meeple can place in each spot. You turn in resources in various combinations to earn victory points, but the amusing difference is that your resources are not different flavors of material like stone and wood that you spend to build structures, but different flavors of adventurer like wizard and cleric that you spend to complete quests.
The main difference in dynamic is that you can build new buildings, which give you new options for meeple-placement and which can have a big effect on which resources and actions are available. Whichever player built the building also gets a rent (from the bank) every time someone places on it, so there's some strategy in whether you want to use a building if it means so-and-so gets a free cleric when you do.
The buildings and the quests both come from a small pool of available options. The quests range quite a bit in both value and difficulty. There are even obstacle quests that you can play on other players which they must complete before they can complete any other real quests.
You track victory points as you go, but there's also a little bit of hidden knowledge, in that everyone has an secret identity card (one of the titular Lords) that gives you bonus VP at the end of the game for having completed certain flavors of quest. I like this, because I think it keeps you from getting too bogged down in spoiler-strategizing in the final rounds. You may think that you know who's in the lead, but since you can't be certain, there's no point in spending ten minutes trying to figure out a way of making up a gap of six points; you just do your best and hope.
The theming is only skin-deep. There's nothing particularly D&D-ish about the gameplay; you could change the resources from adventurers to space crystals and the quests to blueprints and have a great game about building widgets on Mars. But the gameplay is good enough that it doesn't matter.
We had five players and three of us ended up within two points of one another. I won (by a single point) after spending most of the game near the back of the pack, point-wise. (I had a couple high-value quests that I didn't complete until late, and a huge pile of bonus points because I had the odd Lord that gets a bonus for building buildings instead of completing quests.)
It seems like it would play differently with a different number of players, and the variety in the quests, buildings, and action cards seems like it would be worth a fair amount of replay value. I definitely want to play it again sometime!