D&D 5E Methods to split the party

[Azurewraith]

https://www.youtube.com/watch?v=PUMCIn2swTU sorry had to be done.

 

[RobofAllansia]

Capturing most and letting the others assist in the rescue is a good way to go. That way you don't make them feel they couldn't avoid it, especially if you leave it to blind luck as to who remains free.