Tendentious |
I swapped the lurking strangler for a vargouille. The lurking strangler is a beholder-crafted creature - how did the Faceless One come to acquire it? It is of near animal intelligence, which doesn't make it a plausible scout. Also it needs to eat, and the nearby food fountain is covered with brown mold. Depending on how long the party takes to reach it, it may have been down there for many days.
The vargouille is the same CR (2), is an independent creature (so it's more reasonable that it has allied with the Faceless One), is moderately intelligent and, as an outsider, doesn't need to eat - it can wait down there indefinitely.