Spirit is the Monk's resource in Diablo III. It was revealed by Jay Wilson during an interview from Gamescom 2010, but he gave only minimal details about it at that time. Much more is expected to be revealed at Blizzcon, in October 2010.
Spirit
Jay's comment from Gamescom:[1]
- Jay Wilson: The Monk has Spirit. That’s the resource we’re happiest with. He came together very quickly. His combo moves generate spirit, and that’s used for signature moves he does. He can’t do them very often. But they’re great attacks, escapes, and some are recovery moves. That one worked out really well.
From this, it sounds as if the Monk will always be able to do combo moves, but will need to do them successfully in order to enable his more powerful, single use skills.
This seems a very generous design; there were only 3 combo skills (and 8 total Monk skills) revealed in the Blizzcon 2009 demo, but all 3 combos were very destructive, and a player could play the Monk quite effectively using only those skills.
It seems likely in the final game the combos will be toned down to be less destructive, making players use the other Monk skills for offense or defense.
Visualization
Nothing is known about how Spirit is shown in the game. It will probably just be a filling bulb, like health or mana, but the color isn't known. Spirit was removed from the build shown in the Caravan movie from Gamescom 2010, so as not to give away the WiP surprise.