This has some fun ideas for mimics and variations to all sizes, plus swarm. I would rate it one star higher but it has some errors that need to be corrected first.

This is a fun and useful supplement to the official LMoP adventure. LMoP was crying out for something like this, by failing to provide a detailed map of the above-ground ruins of Tresendar Manor, which this supplement does. But beyond that, it provides some adventure potential for the area, including combat, exploration, and role-playing material. (Fighty players can just fight through, but clever players can role-play or otherwise avoid some of the combats).

It works as a lead-up to the main Redbrand Hideout (a way to level up a character, if necessary) or as some extra content for a stronger party to help balance the whole area if necessary. It can even be used as a way to build up tension between the party and the Redbrands, if you don't find the standard storyline compelling enough. It also further develops the story of the tragic fall of Phandalin 5 centuries ago. And in a way it's an homage to the classic Sinister Secret of Saltmarsh, with a twist on the "haunted house" deterrent.

This is a worthy product to beef up the standard LMoP, either to give a new DM some more options & guidance or as a way to add fresh content for DMs or players who are going through this adventure again.

I really enjoy the core idea of this product and its implementation. I am planning to use it in my next LMoP campaign. It can be used as a boost to the Cragmaw Hideout adventure, if you want your players to gain more experience (levels) before taking on the Redbrands in Phandalin. However, I will probably use it instead as an alternate, more interesting location for the Agatha side quest.

The language issues have been completely cleaned up.

Contrary to another reviewer's comments, this adventure does not conflict with the official LMoP product. The entrance to the new level comes from part of the Hideout that is approx 25' higher than the front entrance, so the other exit from this new map is at about the same elevation as the Hideout's front entrance. Also, there is nothing in LMoP that states that the Black Spider has only recently arrived. He has only recently encountered the Rockseekers, but there is nothing saying he hasn't been lurking in the Phandalin area for some time (weeks, months, longer?) searching for the Lost Mine fruitlessly (until now). That leaves sufficient time for the Necromancer to have settled in where he is.