Daemon Princes of Chaos from the Daemons Codex have the DAEMON PRINCE OF CHAOS keyword, and I can't find anything that says they've ever had an errata to give them DAEMON PRINCE.
So RAW, you can take as many of them as you like in the same Detachment as Be'lakor.
Only CSM Daemon Princes (and some named characters) have DAEMON PRINCE as a keyword.
Does anyone have any source that says different?
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