Story Timeline:
Beginning and Ending after DH.
Not Canon Compliant.

Alterations to Canon:
Tonks survives the Battle of Hogwarts.
Tonks/Remus? Never happened. Or if it did then nothing came of it.
(I could write pages about why the pairing is stupid, I won't though.)

Harry/Six Other Women.
(My idea: Harry/Gabrielle/Susan/Luna/Katie/Lavender/Daphne)

After the eviction of the Dark Lord's soul fragment, and free of the retarding effect it had on his magic, Harry becomes significantly more magically powerful as well as unlocking an unexpected talent, revealing he is a mildly talented metamorphmagus.

Joining the Aurors sees Harry hand-picked by Tonks to be her apprentice and simultaneously works him through his training as an Auror and learning how to use his Morphing talents. With Harry no-longer 'Azkaban-bait' as well as being a reasonably good-looking guy who quickly learns how to flirt back their partnership becomes more than merely a professional one and a lot more of a sexual one.

Magical Britain gets an unpleasant surprise when the Lady Susan Bones, the rich, politically connected and exceedingly pretty celebrity-status member of the Wizengamot (and staunch supporter of the DMLE), is kidnapped from the Three Broomsticks where she was about to meet with Hannah Longbottom for lunch.

As a result every Auror, Hit Wizard, not a few Unspeakables and many retired law-enforcement and other volunteers are out turning Magical Britain upside-down and shaking it vigorously. But not Aurors Potter and Tonks, because the day before Susan's disappearance they arrested a bloke for kidnapping, child molestation and illegal potions - he has abducted a 10-year-old girl and used Amortentia on her.

Under Veritaserum interrogation they find out who supplied the love potion but if they delay any longer in acting on the intel then the supplier might learn of the arrest of his customer and escape. So instead of joining the search they are Disillusioned and under Invisibility Cloaks in Knockturn Alley waiting for the right moment to run their sting.

Harry, morphed as a suitably inbred and arrogant Pureblood, enters the store followed by Tonks under his Cloak (yes, that one) thus avoiding the scrutiny of the wards. After sufficiently distracting the store-keeper long enough for Tonks to clear the shop-front Harry makes his pitch, using the phrases they learned from the pedophile, and is soon led into the back storeroom where the real - and very, very illegal - merchandise is kept and sold.

After letting the obsequious idiot fill out his own rap-sheet they stun, bound and arrest him before the start cataloguing the contents of his little operation as evidence. While they are at work though Tonks/Harry discover (on purpose or accidentally) a hidden recess in the wall/somewhere, it opens into a passageway leading down under the store.

When they arrive at the end of the passage they discover a room whose walls lined in rune-engraved stones (or other suitably arcane decor), a large silver ring embedded in the floor with nothing in it except a large gaudy bed. On the seven walls of the chamber there are seven doors, six barred and locked along with the one they just entered through.

Prison cells, they realise.

Upon busting the first one open they discover Daphne Greengrass potioned into a sleep and stripped to her undergarments. A quick examination finds her otherwise unharmed, even from any sign of recent sexual activity. A relief considering the daughter of a Lord who sits on the Wizengamot couldn't have been missing very long without her absence being noticed.

Then Harry makes the next logical leap... Susan.

Levitating Daphne out onto the bed in the centre of the chamber they start busting each of the other cells open one by one. The next contains Katie Bell, recently returned to recuperate in England after suffering a spiral fracture playing with the English National Team in the Quidditch World Cup. The next room contains Lavender Brown, the Teen Witch Weekly reporter who once showed up naked in Harry's bunk at the Auror academy looking for 'an exclusive' (on seeing her in her underwear Tonks can't believe he turned her down... Tonks would have done her). The room after that contains Luna Lovegood, which enrages Harry severely.

Fortunately none of them are any worse off than Daphne.

Figuring Susan must be in one of the other two cells they split their efforts. Tonks enters one cell to find Susan and takes her out into the main chamber and puts her on the bed with the other women. Harry however hasn't come out of his cell yet. Cautiously Tonks approaches and enters to discover him pinned to the floor with Gabrielle straddling him and snogging him senseless, her Allure at full strength and having just as much affect on Tonks.

Gabrielle at first reacts territorially to Tonks' presence, stalking towards her and causing Tonks to back away out of the cell, intent on subduing the other woman so she can have her way with Harry (who she was actually in England to see, now that she is of age and intent on seducing her crush). Tonks however proves extremely amenable and pliable to her Allure and Gabrielle realises that Tonks is Harry's lover. On the spur of the moment she decides that Tonks might in fact be an added bonus.

As she begins backing into the cell where she left Harry, leading Tonks with her, she runs into Harry who has now managed to collect himself, gather his wits and reinforce his Occlumency. Tonks continues forwards and Gabrielle ends up sandwiched between the two and losses all control over her allure.

Incidentally this (or something else that occurs) along with the presence of all the components (the seven participants in the prepared seven sided chamber) all within the silver circle laid into the floor, triggers the ritual (though incompletely prepared and incorrectly performed) causing Gabrielle's Allure to become captured and focused by the silver ring and then increasingly amplified by the magic of all the participants - and consequently awakening all the unconscious women.

Several hours of shameless smut later and the ritual runs out of fuel with the exhaustion of every participant and of Gabrielle's Allure. Harry is somewhat mortified by what has happened and his loss of control but apart from embarrassment (largely from what they did with the other women) most of the witches aren't upset but rather relieved to have been freed and that the creep who abducted them wasn't the one they slept with. In fact for Luna, Katie, Susan, Lavender and Gabrielle getting Harry into bed was actually something they'd either considered before, secretly planned to do or would at least consider a lucky fling.

Daphne finds it exceedingly more awkward. She's been attracted to men before but never acted on those feelings considering her long-term relationship with her lesbian girlfriend Tracey. Before they leave they decide on what they will and won't tell the DMLE and soon everyone is back at the Ministry giving statements. Afterwards however they are all sent to St. Mungos for examinations where a healer, sworn to secrecy, is given the whole truth.

The effects of the ritual are almost impossible to determine with the medical charms the healer has at her disposal and it's Tonks who suggests that they seek out Hermione's help, having joined the ranks of the Unspeakables as a researcher. Needless to say Hermione is blown-away by the revelation of what happened - as well as extremely aroused by the recount of it, especially by Lavender, Luna and Gabrielle who seem intent on sparing no detail.

Hermione takes her first sets of readings and measurements so she can work out some experiments that might give them answers, a process that might take a while. A day later though one symptom becomes obvious, the same ritual-amplified, inhibition-destroying Allure that precipitated everything keeps occurring to Harry and one of the six witches involved - each one in sequence. Only sex between Harry and the witch who is under the effect will break the spell and over the course of the next six days Harry beds each of the witches again.

Daphne is, again, conflicted, she told Tracey about what happened and Tracey while a little unhappy told her there was nothing to apologise for, since Daphne wasn't in control of herself. But that was before it became apparent it would happen again. What's more is that Daphne enjoyed it the first time and her one-on-one with Harry was incredible, in fact she's wanting Harry even when the ritual isn't playing a part at all... or is it? What if it's sharing the desire that others, like Gabrielle, Tonks or Luna (all of whom desired Harry beforehand) and these aren't really her feelings?

Hermione's research progresses, she studies the chamber where the ritual took place, trying to discern the original ritual and its intent. Performing more tests on each of them, she devises several experiments to test the magic of the ritual... that require her to observe them when they are under the influence of the recurring ritual effect and even when Harry and whichever witch is affected are 'counteracting' it. All this stimulation combined with her already existing sexual-tension with Harry (and Tonks who has flirted with Hermione and goaded her a lot) really starts to get to her.

Eventually Hermione figures out that Harry and Gabrielle are two 'poles' of a magical-effect and that the other witches are conductors of a magical bond that is cycling between the wizard and the Veela. She even figures out how it might be broken, by breaking the bond between Harry and Gabrielle. But everyone one of the other witches is adamantly against that, even at the risk of staying in their current situation (even Daphne) considering how close they've grown to the Veela and how they've seen her happiness at being with Harry.

The alternative, Hermione informs them, is somewhat more radical. They need to re-enact the ritual again... only this time they need to basically isolate the others from the bond between Harry and Gabrielle, which will mean that her Allure and his magic won't be imparted to them, though there may remain a connection of some kind. There's a catch to it though, there will need to be one additional component to the ritual, which will be added as the 'circuit breaker' who 'grounds' the other women out of the bond... another witch.

Hermione declares that she is more than willing to serve in that capacity.

Another installment of unmitigated smut ensues but this time with Harry and seven witches.

Hermione didn't inform the others that there was a risk that she herself would be caught in the bond between Harry and Gabrielle while freeing the others and now she's in the same boat that they were in. Regardless, she doesn't seem in a hurry to try and remedy the situation.

Having been released from the ritual's effects the other witches are free to go about their own lives, their old lives. However over time each of them eventually, of their own free will, return to Harry, Gabrielle, Tonks and now Hermione. Even Daphne with the blessing of Tracey, who accepts Daphne's feelings for Harry are now quite evidently real and not caused by the ritual, who is willing to share her with the wizard.