TL;DR: Playing as an alchemist, I found the Lone Alchemist escort quest twice - the second time upon entering a known location.
After finding and completing the Lone Alchemist escort quest a first time (Level 3 of Trollmire), I eventually entered level 2 of the Ruins of Kor'Pul.
After some heavy fighting I retreated to the previous level to recreate my golem and went back downstairs - only to find the Lone Alchemist once again.
Every run has 9 escorts. Which type the escorts are is not limited (meaning you could get 9 alchemists, if rng decides so. Exception is Tinker is limited to max 1 appearance per run).
As for the escort showing up in an already visited floor: If there is no valid path to the exit portal upon entering a floor (for example doors in the way), then the game will not generate the escort. However, once you go through the floor and open the doors, there is now a valid path so the next time you enter that floor, the escort will spawn.
Ps. I moved this topic to ToME 4 bugs.
Friendly Neighbourhood Moderator, moan at me for a teleport if ya get stuck.
