Mandrakes as alternative horrors

[addamsfamily36]

I also hate the plastic horrors. I ended up using EM4's Pipers of Azathoth minis myself

Unfortunately i play far too often in Official GW stores/events to risk using other miniatures.

[Rev. Tiberius Jackhammer]

Mandrakes would be a decent stand-in, they look demonic and have warpflame, go for it! How many Tzeentch daemons do you have already? If you don't have any/many, maybe theme most of the force after Mandrakes, they could make awesome flamers and heralds with some conversion.

Other (GW-store friendly) options to consider would be picking up the old metal horrors, those things look damn nice. Another (budget) option I went with a while back was to saw up some plastic drydads and stick 'em together at odd angles: