Yeah, pretty much. The idea is every trip into the dungeon you will get further than the trip before it. When I played I would just go floor by floor taking out as many baddies as I could, head back to town and start over again. I would leave nothing alive. You can of course pick and choose your fights but it didn't feel right to me leaving a level with monsters still lurking. After you beat every tenth level you will be given the option to enter the dungeon on that level.
any difference between the IOS and android version? (aside from android is FREE while IOS version cost $1) also is this P2W?