What does Fallen in the Fen reward?

Fallen in the Fen gives a choice of Daewyn's Girdle, 6,150 experience.

Where does Fallen in the Fen start?

It was picked up in Redridge Mountains.

The quest log lists it at level 31.

Yes. Its quest id is not in Classic Era, so it is part of what Forever adds.

World of Warcraft: Forever · quest · level 31 · new since Classic Era

A level 31 quest in World of Warcraft: Forever in Redridge Mountains and turned in to Dorin Songblade. Recorded by 6 players running the addon.

Giver and objectives show once a player with the addon accepts the quest.

Item	Given	Item level	Vendor sell
Daewyn's Girdle	as a choice	33	10s

What does Fallen in the Fen reward?: Fallen in the Fen gives a choice of Daewyn's Girdle, 6,150 experience.
Where does Fallen in the Fen start?: It was picked up in Redridge Mountains.
What level is Fallen in the Fen?: The quest log lists it at level 31.
Is Fallen in the Fen new in WoW Forever?: Yes. Its quest id is not in Classic Era, so it is part of what Forever adds.

What sells at this level, and what to keep from these rewards, is in the level 30 to 40 gold guide.

Source: what players running the addon saw in the quest windows; the quest text itself stays in the game. Every quest seen · Redridge Mountains