Quondam Fount (2012)

From publisher blurb:

The farmer’s son had found an oddity indeed... a rare Ice Gem, of mysterious origin. It came from the old well on the farm, the Quondam Fount.

Something might be Down There.

And since you’re famous adventurers, he wants you to check it out.

This stand-alone adventure will easily drop into your existing game. This product contains full details on the Ice Chambers and the denizens of the realm, as well as an easy system for tracking environmental damage from the bitter cold. It is designed for 3 or more characters of moderate level with standard equipment. Magical weapons are not required, but magical curing may prove critical. Water-breathing can also be helpful.

...and be sure to bring your wits, as well as your equipment.