I dig the monsters in the Planescape release. They're pretty well suited for adventures in and around Sigil and the Oustlands.
That being said (plug plug), if you're looking for MOAR MONSTARS to populate your infinite planes, check out Monsters of the Infinite Planes! I'm pretty happy there's not a huge number of dupes between my book and the Planescape book, mainly because the Planescape setting wasn't (isn't yet) available on the DMsGuild - but the planes are generic enough to be separate from the setting.
Monsters of the Infinite Planes - Monsters of the Infinite Planes Multiverse of Monsters and Adversaries Fully bookmarked PDF! Color interior art! Crack o
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