Review of Sargolis
In the form of the Goon Deeps, I have extensive playtest experience of Sargolis. I and the other player found the basic mechanics engaging and easy to understand. We thoroughly explored the Deeps, vanquished the lich, and then used the mechanics to embark on a prolonged and still ongoing surface campaign, which included another delve into my own procedural dungeon. That game has been running for fifteen months, demonstrating the viability of the rules for long term play.
Regarding long term play, the Goon Deeps are a procedurally generated and self-stocking MEGAdungeon. In several months online play, we were fortunate to get down to and dispatch the lich only by the luck of finding several downward exits. I could imagine the game taking a long time to get there. This is something that could be shortcut by group consensus (if "winning" the dungeon is important to the players), or alternatively it is something that could make the Deeps portion of Sargolis a satisfying narrative linchpin.
Our game left Sargolis before Levi added the City Above section. It looks like a very promising addition, with a lot of potential for long-running political intrigue sometimes punctuated by violence. Perhaps we will return to the city, now that more details have been filled in, and seek to obtain greater knowledge of the strange magics of the Masquers ... our group's Erudite so far has only dabbled in tomes magic, a thing we invented / stole from other rules. The magical masks of Sargolis, which were present but not so fully realized in Goon Deeps, are quite interesting. The three dominant factions, which vie for full control of the ruined city, also provide a lot of narrative potential.

