The level 30 quest for Knight's is the Red Knight's Shield. Here's how it works in a nutshell:

First, you must speak to Marc in the desert to accept your quest.

Marc sends you to Gunter, who will tell you to get a claw from an Arachnevil Elder. Once you give the claw to Gunter, he will give you a Red Knight's Sword.

Gunter will send you to retrieve a Secret Room Key from a Bugbear which opens a door near Orim. This door leads to NPC Jim.

Jim tells you to go talk to NPC Gerard (in Silver Knight's Town) so you can get a Potion of Revival. Gerard will tell you to take the Road of Pain quest, however, this time, you can only take a Cure Poison Potion and a Red Knight's Sword and you must kill a Ramia to get a Ramia's Scale.

Gerard gives you a Potion of Revival, which you take to Jim. Jim will give you a Letter of Thanks, which you take back to Gerard. Gerard will give you Shield of Red Knight.

Shield of Red Knight doesn't seem very interesting. AC -2, Weight 50, Knight only. However, it does seem to hint at some kind of Red Knight's Set in the future.