It's hard for me to rate this because to be entirely honest it's either 1 star or 5 depending on your party. If your party is full of power gamers, well built characters, or has exceptional synergy you'll have a blast if not you'll see your players laying on the ground every single fight.
We had a monk 4, Ranger 4, Pregen 4 cleric, summoner 4, eventually bard 4.
Before the adventure
Before the adventure I made sure to mention that season 6 is the year of the sky key and that tech, robots, and constructs were prevalent in the season.
A few people bought adamantine weapons and even the archer got a few adamantine arrows.
I liked the introduction to the adventure and pre fight story. I love RPing Nigel.
I've never seen a first encounter have the same CR as the final boss and be of comparable difficulty. We had 4 people so they didn't get a surprise round. This fight should be a single advanced gearmen not 2 normals. It's high tier incarnation being even worse.
Round 1 they step in and the robots tell them to halt going into init. The party wins (not the cleric, he got a 2) and the party charges. The first monk charge misses, the arrow crit threats but doesn't confirm. The two robots drop the monk to single digits. The cleric comes to heal and the robots see it. Being highly intelligent I assume undoing the previous turn of actions would warrant the attention. Unfortunately after another turn goes buy the cleric is down. The party dances around single digits with less than 30 HP remaining among all players. A lucky crit the turn after the second gearmen heals finishes the fight before he knocks down or kills someone. It would have been very easy for me to TPK the group with this encounter and it needs to be looked at. All of my group save the summoners pet had adamantine weapons/arrows.
After the first encounter (like last round) one more person showed up and we let him join because well we could and I don't want to send people home for no reason. The wand loot also feels super random.
Everything before the final encounter
The mine thrower was skipped due to them ignoring it (secret passages) and time.
The space ship girl was diplo'ed out of her rocket by the bard (Like high 30s before aids). They searched the area.
The blob encounter is like really weird. I understand it's thematic but it takes a long time due to spacing. It also baits out remove disease from the wand potentially removing it from use for the final encounter.
The two creatures prior to the blobs are cute but at low tier really not dangerous. They gave the players a chance to have a fun easy encounter in STARK contrast to the first and last ones.
The final encounter
Oh god where to start.
First off it's the first encounter substituting 1 gearmen for a nanite SWARM.
Once they saw the gearmen they annihilated it dumping everything they have at it. It only lasted 1 hit (Which I rolled max on nearly knocking down 1 person.) They managed to force it out after knocking down pendelton. They stood in swarm formation (Which I mean 4 people in a 4 foot squares) and a fair number failed the save. They eventually haste grab pendleton and throw alchemist fires at it as they run through the museum. It was really really obnoxious trying to wear it down.
Whoever came up with nanite swarms needs to be dealt with. How short of having a wizard or sorc who loves fireball are you supposed to kill it? It will win most fights unless they fail the possession saves in which case our monk would have TPK'ed the group.
TLDR; If you've got a strong group this is a fun challenge. If not it's a near TPK. We had someone who had never played society before at the table. I really hope we didn't scare him off with this adventure.