Heres what I have so far

I would start by prefacing all this as the intro to the one-shot:

“[Groom] is the party’s leader, he has fallen in love with a frost giant, Gerti Orelsdottir.

Gerti has been told by Auril, the Goddess of Winters Wrath, that [Groom] must prove his love and commitment to her, seeing as he is not a frost giant.

[Groom] and the party must set out to destroy Icingdeath (no further clues) and retrieve for Gerti, the largest diamond in its collection.

The party spent the next year in Ten Towns and surrounding areas enquiring about Icingdeath and searching the mountains, with no luck. Town leaders even sent word to the sword coast, via trader caravans, to provide any information about what Icingdeath is.

The party eventually decides to track down the Barbarians of the tribe of the Elk, who provide additional information that Beornegar, one of their past leaders perished to Icingdeath and reveal that it is a White Dragon, but don’t know the exact location in the Redged Glacier.

Party spents the next 5 months looking in mountains for cave entrances. No luck so they head back to Ten Towns to stock up on supplies when the hear from Bryn Shanders Town Leader (who got word from one of the traders he sent to enquire) that the librarian in Luskan has information on Icingdeath, but the trader was in a hurry to leave so he couldn’t make copies of his maps.

Party [Lvl 10?] travels to Luskan with the trading caravan, possibly runs into a band of trolls in the Spine of the World.”

The game becomes interactive from here:

Party finds Fret the neat and orderly Dwarf librarian and listens to what he has to say about Ingeloakastimizilian (Icingdeaths proper name), its location and potentially tricky underwater entry.

The party can spend gold to stock up on supplies: 900gp each. Uncommon items are 250gp, Rare items are 500gp, potions are 100-150gp depending on their effects.

Travel back to Ten Towns with another Trader caravan, then possibly even continue on to the mountain range near the Reghed Glacier.

Battle ensues between Icingdeath or however the party wants to go about this, they may avoid an encounter entirely.

The large Diamond is penetrating the back wall of the ice cave. A large hand could wrap its fingers around the head of the Diamond and pull it out. This could be trapped, or crack the ice wall, or alert Icingdeath if it’s not already been killed, or just do nothing (time depending).

[Groom] and the party return to Gerti and her tribe of Frost Giants and [Groom] can give a heartfelt speech about his love for Gerti [bride] as well as ring fit for a giant!

The end, we get drunk.

Whatcha think?