The Lost Temple of Forgotten Evil is a level 4-6 fantasy adventure by +Kevin Watson. It is part one of the Hauntings of Hastur series. I own one of the print OSR/5E kickstarter copies as well as OSR/5E pdf and the Pathfinder pdf.
Having to do with Hastur, the adventure obviously has a dark feel to it, but it's definitely not too dark or weird to be added to a standard D&D game. The adventure could be placed on the outskirts of any fantasy kingdom with little work.
While I've not ran through it, I really like it. The author has included a great mix of well-balanced combat and non-combat encounters. While there are definitely times you have to fight, parley is important too.
A majority of the foes faced by the party will be human. This surprised me considering Hastur's involvement, but given the plot, it does make sense. I hope to see more eldritch horrors in part two.
The pdf's come with an extra pdf that is just illustrations and maps from the adventure. This was an excellent touch and I wish more companies would do this with their releases. I know the art style isn't everyone's cup of tea, but I think it works given the flavor of the adventure. I do want to talk about the portrait of Fredu for a moment. He resembles Robin Williams.Williams was a great man and avid gamer, so it's cool. I appreciated it, but it actually kind of made me too sad to read the adventure for a bit.
So the important question, should you pick up this adventure. I say most definitely.
If you're curious about the style, just out the free sidequest: River Crossing.