With Mass Effect 3, BioWare's gone a little bit "Civilization". No longer will you, the upstanding/faceless/dastardly Commander Shepard, be called upon simply to stroke crewmate egos and polish off their unfinished business; nowadays it's all about the bigger picture, a picture shortly to be set on fire by invading Reaper squadrons.
All your diplomatic cunning will be put to the test, as races clash over vested interests and millennia-old grievances. The Krogans have been at the machismo juice again, but you know the second you take your eye off the Volus they'll be trafficking sentient lifeforms like there's another galactic Dark Age round the corner (there is). And don't even get us started on the Asari. Goddamn hippies, sleeping and shooting their way around the galaxy, secure in the knowledge that everybody they piss off will be dead by the time they hit puberty.
Many of the game's species-affecting choices will, we suspect, take the form of relationships with key individuals, including returning Mass Effect squadmates, but reading up on the races themselves is probably a good idea. No, don't go to Wikipedia. Scroll down the page. We're a-bubble with insights and predictions. Beware Mass Effect 1 and Mass Effect 2 spoilers.
Ah, the Krogan. Sexually handicapped Klingons who only see eye to eye when they're gunning people down point-blank. They're either Mass Effect 3's biggest asset, or Mass Effect 3's biggest liability - bear-sized lumps of muscle, back-up organ and reflex with an appropriately brutal attitude to inter-species politics. Bring them on side, and they'll chew through Reaper husks like killer whales through plankton. But get on their nerves, and you might as well head-butt a wall till your face falls off.
The fate of the Krogans is tightly bound up with those of the Salarians and Turians - the former of whom developed a species-wide infertility bomb, the second of whom used it to put the Krogan Rebellions out of commission. Winning their allegiance will undoubtedly mean resolving this long-standing enmity by either (a) persuading the Krogans to live with a drastically reduced birth rate, or more likely (b) persuading the Salarians to finish off the Genophage cure researched by Mordin Solus' assistant Maelon. Achieving (b) would probably require that Shepard (c) convince the Krogans to stop treating the galaxy like a punching bag, and in this regard, the efforts of old Normandy squaddie Wrex (or, depending on your actions on Virmire, his brother) to unify Tuchanka's warring clans could be crucial.
There's also Grunt's renegade strain of tube-grown Kroganism to account for. His conventionally born brethren entertain mixed views about his parentage - responses on Tuchanka were "divided" to say the least - but as a distillation of all the best Krogan traits, he makes a promising figurehead. Read Matt's enormous Mass Effect 3 characters piece for more.
When's the last time you had a conversation with a Volus which didn't devolve into racist back-biting or fawning attempts to put you off your guard? Oh right, there was that guy hopped up on biotic drugs on Illium. Full of hot air in more ways than one, the Volus have a species-wide insecurity complex; they're convinced that all other races save their patrons the Turians - and particularly humanity - are out to rob them of influence and steal their profits.
As tubby sacks of gas, the Volus don't bring much to a stand-up fight, but as chronic wheelers and dealers, they're the nearest thing the galaxy has to Switzerland. Coaxing out their loyalty will be vital if you're to fund the war effort, and we can think of no better way to do that than via Turian strong-arming. Speaking of which...