I have run this one twice now, once at a convention and once for my AL group. Overall, this can be a slog if the players go combat heavy. So I made some changes to improve speed when I ran the adventure for my group that was working through these sequentially. So take my notes below for thoughts:

First, I highlighted that the portals, the elder brain dragon, and the psychic backlash from the events at the supreme forge have made the city even more weird and dangerous. So everyone is more paranoid. I kept the wild magic potential increased- any levelled spell had a 10% chance of a wild magic surge. Wild magic sorcerers at 15%. Cantrips & rituals were fine, but even spells from magic items counted. This had the effect of making them plan more. But it also gave me room not to overly punish the players in part 3- the Thayans were cautious as well. This also made the second encounter make more sense- it highlighted the weirdness and danger of the place. It also opened more options for distraction tactics if they embraced the wierdness.

Second, and because of the first one, Thayan patrols brought along Thayan (aeorian) abominations. Story wise, to provide some non-spell magical support. But mostly because they are cool. I also used these as reinforcements in part 3 to provide variety other than “Oh great, more mages and fighters”. The nullifiers in particular help manage wild magic surges from the Thayans once they arrived, allowing the enemy to amp up the number of offensive spells being cast.

Third, I considered the entire facility as “Sparky’s” lair. As such, it was a noisy, smoke filled place. This provided the lightly obscured condition, which allowed the party’s sneaky people to scout the interior and first floor while the rest hid. This kept the story moving and provided some interesting story moments where they had to decide whether to help the slaves and risk being found out, or leave them and complete the mission. The upper floor was less smoky and noisy, but still enough that it made the mages with improved invisibility nearly impossible to track. Which was fun for everyone.

Lastly, I had the”Sparky” show up on round 5, to get them moving to the exits. It took 4 rounds to squeeze through the doors and up the stairs. This allowed the party an opening to escape, if they could get around it and back to the first floor.

I rated this 3 out of 5. My players enjoyed parts 1 and 2, but struggled with 3. But in each part, I had to make some adjustments in order to make it flow in an entertaining and timely manner. In all parts, having a sidekick is critical for helping move the plot along. It keeps the party focused in part 1, can help with options in part 2, and maybe help with a side-portion of part 3. If the party hasn't met the three before, let them interview each. If not, I suggest picking one that fills holes in the party. In part 1, the NPC can help keep the party focused and avoiding any number of pointless combats with wandering afflicted. Having someone who knows the other NPCs also provides motivation to fix, not kill. Which speeds things up. However, the section really needs to be re-organized. I found myself flipping through multiple pages because you start with a cutscene, then have to flip to room 4, then back and forth for information. For clarity, the room you start should be room 1, and keep the lower level (where the important parts are) immediately following it. In part 2, There are many things you can do to speed things along. Let the characters focus on finding clues and use the NPC to 'fill out the chart'. That avoids issues if you have a group that does not like math puzzles (most groups, sadly). The pit portion can be wildly frustrating because the creature is not a beast, so speak with animals does not work. I highly recommend adding "understands common, but cannot speak it" to its stat block, and a note saying that anyone with a shard CAN communicate with the creature through its chew toy. That makes this one hugely fun. The party's ranger was nearly cuddled to death. The last part can be tough, so I made the judgement call that a DC18 Survival roll could give the party advantage against the exhaustion effect- but only because our ranger asked if they could figure out a way to make the climb easier.
In part 3, having the NPC allows the party to save the other NPC without losing efficiency- have their NPC do it. I had one player that never made a save the entire combat. That was brutal. So I had to make some adjustments to how things played out. Once anyone made contact with the ice, I ended the compulsion effect. I also changed the effect so that those stuck lost their move action and were essentially grappled by the wall, taking damage. This allowed them to take an action, at least, and feel somewhat involved. Since he was a sorcerer with Misty Step, I had planned to re-institute the compulsion effect if he jumped away, but he never thought to do so. But it was still a slog since the characters didn't really ask the slivers about what they were actually supposed to do. Again, this is where having the NPC came in handy.
Overall, this was a great module, if it runs a bit long (4.5 hours with rewards, etc). But each section needed something to make it run more smoothly.

Since this is the first of the Tier 3, it is possible that some or all of the group have not played the lead-up tier 2 modules. Luckily, the module provides an excellent way to do exposition dumps- the sidekicks! I strongly recommend allowing the players to interview all 3 and pick the one they like the best to go with them. Then, they have a walking catalogue of all that has come before, which adds SO much to this module.

Story-wise, it is a straightforward exploration mission for the most part. It relies heavily on DM narration to build tension and atmosphere. So preparation on this one is perhaps more important than most. If you can get across the utter alien-ness of the city, you will captivate the players. I recommend over-using the visions and temporary insanity charts.

From a module standpoint. the only thing that needs work are the maps for part 3. It is confusing how and where the players enter the complex. The complex expands in further modules, and some better description is needed to explain why certain areas are not accessible. Particularly important because the players receive story awards based on what they do to secure the site.

Most of what was said below is still true. So: 1) Rework the DM maps and player maps. Staircases are missing, names on player map need to be on DM map so you can understand where they are going, and so on. They are terrible. 2) Stress, over and over again, how suicidal it would be to try to do this during the day. Otherwise, expect never-ending combat.
3)

This is another good stand-alone Tier 1 adventure with a straightforward mission. I've run it once with 6 players, 4 4th level, 2 1st level. It was easy to keep the encounters balanced to challenge the 4ths but still allow the 1sts to feel as if they contributed. There are excellent opportunities for all three pillars to be enganged- exploration, combat, diplomacy. While it is stand alone, I found it easy to develop a link between INT01,02,and 04 to this one. I recommend running this one last if you plan to do it as a series. It is easy enough to tie the assault on Elventree to the mage and book theft in INT03.

That being said, out of the 4 INT modules, this is the one I struggled the most to run. In an effort to keep things simple to run, the module hand-waves the travel distance into a series of encounter way-points. Biut the distance is not insignificant, and SHOULD take multiple days, requiring multiple long rests to avoid exhaustion. I recommend to any DMs to develop their own charting system for successes and failures.

The beginning of the second section didn't make much sense to me. The village should evacuate no matter what with a huge army bearing down. So I added that one of the goals of a Thayan battleplan is to take as many prisoners as possible. Slaves and pre-undead are highly valuable. The gnome chief knows this. So I chaned the choices to a) hold the line in the main common area to delay the enemy long enough for the villagers to escape or b) screen and protect the villagers as they move through the forest.

In the second section, my group chose the chase. Now, chases are notoriously difficult to run in 5e. They are hard to visualize, and require a lot of hand-waving of distances, comabt reach, etc. And this one has a few problems that need specific adjustments and changes to allow for quick adjudication to keep the chase moving. The module states that the NPC mob will dash each round. That can quickly put them way out of reach of the enemy to hurt and the characters to help. So I implemented a statement that if a player wasn't within 60' of the NPC mob, they rolled at disadvantage on the complications table. After all, the purpose was to guide the NPCs and keep them safe. I also said that if the NPCs took damage that round from a complication, they could not dash. So I had to alter some of the one-time benefits from increasing movement to allowing a dash that round. I also had to adjudicate the use of the Darkness spell during a chase. The quick way I did it was to say it imposed disadvantage on the complications roll for anyone passing through it. Lastly, I hand-waved variable movement rates and let everyone move in 30' increments if they had less than 30' movement rate. I described this as breaking up the mob into groups and letting the slower-pace people guard the slower-pace NPCs as they moved along. But the relative distances were still good. That allowed me to keep everything at 30' increments, which made tracking MUCH easier.

Overall, my players really enjoyed this entire module. The opportunity for skills and diplomacy to effect gameplay early was well received. The chase in the second part was chaotic and challenging to manage, with hard choices to stay together or leave those who fall behind.

This is another excellent stand-alone fetch quest. Go somewhere, get something, complications ensue. The module itself plays through in a clear manner, with the sequence of events happening in whatever order the players encounter them. The final battle can be quite difficult given the building design. There is a choke-point that can become quite problematic depending on initiative order given that there is a timer on the final battle. My players nearly lost becasue of their inability to get through quickly. Overall it will run longer than some of the others if the players are not extremely clever. In addition, setting the atmosphere early is key. The module is muddled a bit on this one- is is stormy or bright moon-lit night? I reccommend reading it through carefully and writing notes about opportunities to set tone. The NPC are supposed to be creepy (undead), but the area lends itself more to unnerving (lycanthropes). Select how you want to make the characters think and make sure the interactions match appropriately. I leaned into the lycanthrope tone more in my interactions. I used this once, as part of a Adventurer's leage through-line with INT-01 & INT-02. It makes sense for this to be part 3. But I had to make some changes to the background. In INT-01, they encountered a red wizard. I added that they found a clue to a group he hired to raid a tomb a few days away. In INT-02, the stopped the group from raiding a tomb. I added that the Harper agent sends them to Candlekeep to get more information. Part 3, I added that to get the information, they needed to run an errand. Which set up Int-04. And the wizard at the end I changed to be the same one from INT-01. And they had a note that said after they gathered the books, they were to rendezvous outside Mulmaster to support an offensive operation in the Moonsea area. Which leads to INT-03.

This is mostly a dungeon crawl, which can be a good thing. It is largely stand-alone, so if you are planning to use this as a series, you may need to make some modifications to the Call to Action and part 2. For me, I used a note found on the villian on INT-01 that said he was to check on a hired crew exploring some ruins. That was enough.
It can be easy to finish in 2 hours if the players choose to avoid exploring some areas. So taking time to improvise and expand upon a particular social interaction is recommended. In addition, would reccommend any DMs clearly think through how they want part 2 to proceed based on what information is in the module. As I read it, part 2 turned out to be a wasted opportunity for exploration because of the event that happens right at the beginning. So I changed a few things so that the area was obscured so the players could not see which way the opposition fled and had to make choices and explore. Overall, it can be played through as a stand-alone with minimal changes, or adapted quickly for a larger campaign.

This module plays well on its own, but can be a bit short if you have charcaters who manage to avoid all combat. The important part for the DM is to have a solid handle on all of the NPC and thier motivations. Being able to clue the players about who is doing what is critical to them solving the issue. I used it as a starting point for an Adventurer's League thru-campaign based on the Red Wizards. So having the antagonist escape worked well for me. But since my players pushed through it quickly, I allowed them to chase / figt some of the bad-guys even after they succeeded. This allowed me to drop a clue that took them to INT-02 (which I ran the following session).