La Divina Commedia, Assembly Big Top <br></br>The Golden Pavilion, Garage <br></br>The Complete Lost Works of Samuel Beckett..., Assembly Rooms <br></br>Latin! Gilded Balloon Teviot <br></br>Outlying Islands/Iron, Traverse

Dirty devils, dead playwrights and dodgy pedagogues

More and more, Edinburgh's annual explosion of drama is having to compete with major London openings. The capitals are now fighting tooth and nail for theatre-loving tourists. However, the ballsy spirit of Scotland's Fringe Fest proves both fierce and fun. Take La Divina Commedia, performed in a circus tent by Russia's physical troupe Derevo. This is a wordless dance of death in a murky primitive/modern hell.

On one level, it is a deliberately crowd-pleasing spectacular featuring gothic demons, a clowning angel, and snowstorms of twirling, glittery paper.

Yet Derevo are also bold and dark. They look like prison camp ghosts with their shaven heads, and their dreamlike visions are haunting. A despairing girl in a night-dress is suspended in mid-fall, hanging by her toes from a high ledge above you. A mocking devil – squatting in another tower – frenetically rubs himself with straw. Elsewhere, a tortured naked soul is pushed into the ring like a sacrificial cow, with a clanging bell tied to his tackle. He bucks in agonies which look suspiciously like erotic ecstasies. This could be dismissed as a calculated "shocker" – Derevo's Christian symbolism can be heavy-handed and the last 10 minutes are a shambles. Nonetheless, this ensemble's intensity and ragged beauty – paired with a pulsing, wailing soundtrack – grip like a vice.

Over at the pioneeringly global Garage, The Golden Pavilion is experimental fare from Japan's Company East (whose Medea thrilled some critics last year). This time they dramatise Yukio Mishima's tale of an apprentice priest whose youth is marred by a stutter. He becomes obsessed with a beautiful temple, then madly torches it. The cast's writhing and kicking choreography (welding Noh with modern dance) is frighteningly visceral. But heaven knows what anyone was saying – or screeching (I believe bits were in English). Something about burning the Golden Dimple?

Moving swiftly on, Ireland's revered guru of minimalist gloom comes in for a pasting in The Complete Lost Works of Samuel Beckett as Found in an Envelope (Partially Burned) in a Dustbin in Paris Labeled "Never To Be Performed. Never. Ever. EVER. Or I'll Sue! I'LL SUE FROM THE GRAVE!!!". Some of the skits are milked in this spoof in which a squabbling actor, director and stage manager present the amazing "finds". Nevertheless, the ebullient cheekiness of Beckett's supposed juvenile puppet play, Happy Happy Bunny Visits Sad Sad Owl, is irresistible. Donning a waist-length peroxide wig, Ben Schneider is also outrageously funny in the hitherto unknown pop-rock version of Rockaby. Pouting at us like a nymphomaniacal Miss Haversham with Bread's shamelessly sentimental ballad "If" playing on a loop tape, he croaks "More" until the audience are on their knees. One punter literally fell off his seat laughing. Beckett's rigorously protective estate may not be so amused.

Courting controversy another way is a revival of Stephen Fry's early play, Latin!, about a grade-fiddling public school master, Mr Clarke, who takes one of his underage boys for a lover. Mr Chips he ain't. Last week, Radio 4's Today programme picked up on a local Tory's protest campaign about this show's comic treatment of paedophilia. Frankly, it's hard to get really hot under the collar when the jokes mainly involve Clarke (sarcastic Mark Farrelly) picking on audience members about their lousy prep. That said, Fry is problematically indecisive, morally sitting on the fence. He satirically condemns the covertly corrupt institution and has Clarke himself saying he's a cold-hearted monster – but that's retracted and the teacher and his apparently wholly willing amour run off to live happily ever after. The adolescent is, evasively, discussed but never seen. The acting, by the by, is nothing to write home about.

Now to the Traverse, the Fringe's most prestigious venue for new plays. David Greig's Outlying Islands, directed by Philip Howard, is rather stiff. On the brink of the Second World War, two young chaps from Cambridge University arrive on a remote Scots island to conduct an ornithological survey. Robert and John bed down in an ex-pagan chapel and, Lord of the Flies-style, civilities are soon cast aside. The puritanical owner of the rock bites the dust and his daughter, Ellen, is left with the voyeuristic lads.

Greig's overarching ideas are strong, starting with the pull exerted by remote islands and the allure of off-limits behaviour. But sometimes his analogies – not least the bird-watching, feathered and otherwise – seem schematic. The production warms up commendably with Lesley Hart's excellent, increasingly freewheeling Ellen and a bruising, tragic conclusion.

Nevertheless, Laurence Mitchell and Sam Heughan's initially wooden performances as Robert and John need sharper definition.

Written by Rona Munro (who wrote the screenplay for Ken Loach's Ladybird, Ladybird), Iron is the real hot ticket. In this quietly arresting prison drama, a privately unhappy career woman called Josie seeks out her estranged mother, Fay, who is serving life.

You're kept guessing about whether Fay murdered Josie's dad and, if so, why. Who is naive and who is protective or ensnaring also become complex questions. Fay (gaunt Sandy McDade) looks like a starved fledgling and wants to live vicariously through Josie, not rake up the past. Josie (physically sturdier Louise Ludgate) obsessively asks Fay to feed her the childhood memories she has expunged.

Structurally, Iron is plain, almost dour, with extended dialogues and two warders to complete the equation. As director, Munro doesn't flinch from physical stasis and Anthony MacIlwaine's set of towering grey doors is equally austere. This allows you to concentrate on the riveting performances, the disturbingly slippery conversations and the morally challenging shifts in sympathy. Catch this.

'La Divina Commedia': Assembly Big Top (0131 226 2428); 'The Golden Pavilion': Garage (0131 221 9009); 'The Complete Lost Works of Samuel Beckett...': Assembly Rooms (0131 2226 2428); 'Latin!': Gilded Balloon Teviot (0131 226 2151), all to 26 August. 'Outlying Islands' and 'Iron': Traverse (0131 228 1404), both to 24 August