[Baalz]

Demon knights are very cool, but you have to keep in mind the opportunity costs. Pans are awful big mages to be summoning line units one at a time. The demon knight costs a good bit more than 5 blood slaves in this case. 10 demon knights is a useful force - but it costs you 50 blood slaves...and 100 research points, plus 350 gold in Pan upkeep if you've delayed transformation to get them, plus the gold you tied up in the initial recruitment of the pans. Demon knights are indeed solid units, but in most situations they're comparable to your buffed centaurs so don't bend over too far backwards to get them.