Mordenkainen's Tome: what monsters are in it?

[Beleriphon]

Zelekhut
Pursues fugitives from justice. I fear that one migth invite derision. Oaths and pacts can be played as having mystical weight, but when the baron of Pravoka puts an arrest warrant on you and suddenly a winged mechanical centaur appears from Mechanus to catch you... I don't know, maybe it is the power of nobility, or the spirit of a nation, directing this hunter on you?

I am trying to think of a shadowfell creature with the beast type, but I got nothing.

I think its cosmic justice. Like you murder Baron von Parkova's whole family, you get an bounty hunters after you, come back murder the Baron and then declare yourself (or are perhaps declared) ruler of Parkova thus forever avoiding justice. I think it takes a pretty heavy load of avoiding justice to get a zelekhut to chase you.