Microsoft announced back at E3 2012 that it was bringing a free-to-play action-RPG to Xbox Live Arcade, then seemed to forget about it. Well, Ascend: Hand of Kul quietly launched yesterday, so give it a go if you fancy murdering monsters without paying a penny, at least to check out its single-player/multiplayer crossover ideas.
Technically Ascend (formerly subtitled 'New Gods') is out in open beta rather than properly launched, but hey! It's a 2GB download from the Xbox Live Marketplace.
Ascend is chiefly a single-player monster-mashing action-RPG, but has some interesting multiplayer touches. Players can see the ghosts of others running around the world, and either buff them or mess with them. See, you're all pledged to one of three gods, and your play tips the balance of the overarching 'Crusade' metagame in favour of yours. So banishing monsters from your game into someone else's is both useful and delightfully cruel.