Deepwood Memorial (5e) (2016)

From the introduction:

Millennia ago, in a time remembered nowhere but in long forgotten books, there was an elven civil war in the Deepwood. It began as a land feud between two elven houses and raged for 103 years. Both sides suffered many casualties. Finally, a great king rose to power and brought an end to the war. To be sure future generations did not forget the cost of civil war, the king had a memorial built as a reminder of the price paid in blood. When the king died, he too was entombed in this memorial, in a secret chamber. The memorial has been abandoned by the elves for hundreds of years now. Since then, it has been looted and defaced by various vandals. Recently, a collapse in one of the rooms exposed a nearby cave system, and subsequently an Owlbear has made its nest here with its young.