Just a random thought......

Masters, mounted upon Dark Pegasi, each with heavy armour, sea dragon cloak, shield and a lance.

138 points a pop. You can fit 3 into a 2,000 point army...

It packs one hell of a punch, and with that 1+ armour, really rather resilient! Plus, dead fast and manoeuvrable. And unless I'm out of date on the FAQ's, you've also blagged T4 characters.