In case you're curious, here's the scoop on Scarlet Cavaliers. Six (6) of them exist in all of World of Warcraft. All six of them can be found only in Mardenholde Keep, which is in Hearthglen, Western Plaguelands.
Two of the six are easily soloable:
- The first one patrols the ground floor of the Keep in the clockwise direction.
- The second one patrols the second floor of the Keep in the counter-clockwise direction.
Two more of the six are soloable through a bug: After you have cleared both patrolling Cavaliers and four Scarlet Sentinels on the ground floor leading up to the second floor stairs, you can aggro Taelan Fordring and the front two members of his Cavalier guard. Run down the ramps, jump over the banister, outside of the Keep, turn left, wrap around the back of the Keep until you get out of combat. Then run back into the Keep very, very quickly, and with luck, you'll be able to pull one or both of the rear two Cavaliers before Fordring and the front two respawn.
The final two Cavaliers of the six are linked to Fordring, a 63 elite paladin mob who heals, has a nasty AoE, and can use Lay on Hands (full-health heal which requires no mana to use). This group is three-mannable: ideally a tank, healer, and a sheeper/sapper.