Cloudgate Dance Theatre of Taiwan, Barbican Theatre, London<br/>Mayerling, Royal Opera House, London

Unlike the Olympics, the annual Dance Umbrella season has never had, and never thought it needed, an opening pageant. But it got one by default this year with the latest work from the choreographer Lin Hwai-Min and his phenomenal t'ai chi-based Cloudgate Dance Theatre of Taiwan.

While Lin's work has always been spectacular – tons of rice rained down in Songs of the Wanderers; in Moon Water he flooded the stage – for Wind Shadow he has collaborated with Cai Guo-Qiang, visual director of the Beijing Olympics' ceremonies. The result is both more collar-grabbing and more political.

The serene first half gives no clue of what's to come. The opening image is of a white kite, held aloft by streams of air generated by fans hidden in the wings. Before long the air is crowded with fluttering kites, or being sliced by dancers wielding room-sized flags. Others appear as pale angels sprouting tall, feathery wings that tremble in the breeze. The smooth, meditative movement slows the heartbeat, and the interplay of air and airy substance is hypnotic.

Enter the shadows: faceless figures sheathed in matt black from head to toe (interesting how simply covering the face and hands gives a sinister effect, summoning burglars or malicious spirits). Yet at first these shadows behave as shadows should, ingeniously lying on their backs to mirror the movements of the standing dancers, their ankles linked. Silhouetted against the white floor, delicately shifting kaleidoscope patterns emerge like complex designs in mosaic tiles.

Little by little, though, the shadows take over, seeming to suck the life out of the dancers they're attached to. They swarm and muster like a plague of giant ants or rats. Or they clump together, their human shapes no longer discernable. At one point the lighting gives their massed, upturned bottoms the texture and colour of dusty boulders.

This is where the aural assault begins, as the sounds of machine-gun rounds and bomb blasts make you want to cover your ears. The giant white flags, still waving, offer themselves as screens for the projection of frantically overlapping images. What might, in another context, be displays of Chinese fireworks are more likely the sparks from exploding buildings, the splatter of inkblots on the back wall the work of a bomber seen from the air.

A programme note says that this is a piece for the post-9/11 world, and when the sky rains black ash, the reference is at its most pointed. What happens next, though, tips the imagination into a terrifying unknown, as smoke engulfs the struggling dancers, followed by the startling formation of a sulphurous vortex which sucks every living thing into its dark centre.

It's a dazzling coup de théâtre, but presses home the extent to which Lin's fine dancers take second place to special effects. Does it matter? No. Wind Shadow is a thrilling extension of Lin's ongoing exploration of the combined power of kinetic sculpture and the elements. It may be more art installation than dance, but it's a knock-out, whatever you call it.

The week's other big-season opener showed dance at another extreme. Mayerling was Kenneth MacMillan's last big ballet, his darkest, and – structurally, at least – his finest. There is less of the padding that weakens his hits Manon and Romeo and Juliet, more of the scalpel-to-the-flesh exposure of human failing. Failing may be too mild a word for what ailed Crown Prince Rudolf, the morphine-addicted heir to the Hapsburg Empire, who in 1889 blew out his brains in a suicide pact with his teenage mistress.

The revelation of this revival, with the cast led by Edward Watson, is the extent to which Rudolf's tragedy hinged on relations with his mother (an impressive Cindy Jourdain), the pair emotionally paralysed by a shared fear of inherited madness. Whether real or imagined, the effects on Rudolf were crucifying, and the ballet doesn't flinch from exploring the full horror of his life's disfunction. The wedding-night duet is virtually rape, Rudolf's taunting of his young wife, by taking her to brothels, grotesquely cruel. His gun obsession, his drug habit, fester unchecked. When he meets his match in the young Mary Vetsera (Mara Galeazzi, giving it all she's got), his end is sealed. The marvel is that MacMillan makes all this watchable, finding a physical language to show a man so far buried in self-loathing that he takes perverse sexual pleasure in his death. Watson turns in a horribly believable performance. The company responds by doing what it does best, finding superb dramatic subtlety in a work of violent extremes.

'Mayerling' to 10 Nov (020-7304 4000)