[Taqwus]

'course, one might note this: in combination with castling, Ghost Riders makes a nasty anti-raider spell as well. Enemy arrives in your province, perhaps by flying or magical means (several Tartarians cloud-jumping in for a visit, say), then get nailed by 5-6 castings of Ghost Riders before they can move away (short of using the Boots of the Planes or Gateway Stone to 'port/astral travel away) or breach the walls.

It's handy against PDs or unprepared small/medium armies; against the larger armies FFTS, Murdering Winter or perhaps even Beckoning can do more damage.