In The Elder Scrolls IV: Oblivion plugin Knights of the Nine Revelation there are a number of unique items, rewards, abilities and improvements that can be gained during the quests. Some of these are quite powerful, whilst others are simply unique decorative items.
Castle of the Nine
The various Crusader Relics will all be improved by the end of Shrine of the Eight. They can be either Light or Heavy armour and either an antique (the original) or polished appearance, both of which can be changed using the Knights of the Nine Revelation options book in the Lord's Quarters of the Castle of the Nine.
After they have been reforged, the Relics have an improved performance over the original ones. How much depends on the player's level, as this is a levelled improvement. The original Relics maxed out at level 21+; the improved ones at level 40+, with, after the initial 1st level standard, an increase in their performance at level 7, 11, 16, 21, 25, 30, 35 and 40.
Boots of the Crusader
The original boots enchantment gave Fortify Restoration from 2 points to 6 points, and the improved enchantment ranges from 3 to 11 points.
Cuirass of the Crusader
Its unenhanced enchantment gave Fortify Health from 15 to 27 points, Fortify Restoration from 2 to 6 points and Resist Normal Weapons 15%. Once improved, Fortify Health ranged from 20 to 52 points, Fortify Restoration from 3 to 11 and Resist Normal Weapons is 25%.
Gauntlets of the Crusader
The standard gauntlets give Fortify Restoration from 5 to 9 points and Resist Disease 50%; the enhanced ones Fortify Restoration from 6 to 14 points and give Resist Disease of 75%.
Greaves of the Crusader
Their original enchantment of the greaves gave Fortify Restoration of 2 to 6 points and Fortify Destruction of 5 to 9 points. Once improved, Fortify Restoration ranges from 3 to 11 points and Fortify Destruction from 6 to 14.
Helm of the Crusader
The helm originally gave Fortify Restoration of 2 to 6 points and Fortify Personality of 25 points. Once improved, Fortify Restoration ranges from 3 to 11 points, although the personality bonus remains the same.
Shield of the Crusader
This originally gave Reflect Spell ranging from 10% to 18% and once improved it ranges from 12% to 28%.
Mace of the Crusader
The mace originally caused Fire Damage of 2 to 14 points for 2 seconds on strike and Turn Undead from level 1 up to level 17 for 5 seconds on strike. The improved mace causes 3 to 23 points of fire damage and Turns Undead from level 1 up to 25.
Sword of the Crusader
The sword originally caused Fire Damage of 2 to 14 points for 2 seconds on strike and Damage Magicka of 7 to 40 points. The enhanced sword causes 3 to 23 points of Fire Damage and Damages Magicka from 7 to 60 points.
Each of the Knight Commanders - the original, named, Knights - commands troops, each of which have a different speciality and a corresponding ability and equipment. By speaking to the relevant commander you can get them to accompany you along with some troops. You can have up to 8 troops plus their commander following you, but only one commander at any time unless the option to enable Multiple Knight Commanders is activated using the Knights of the Nine Extras in the Lord's Quarters.
The commander cannot die but the troops can, although there does appear to be an unlimited supply of them, even if they are killed in combat. They will not resurrect in combat, but after sending them back to quarters they will be alive for the next time they are needed.
You can order the commanders to bring their troops or return them to their duties, follow you or wait where they are and get them to repair their gear. If the commander is in the Castle of the Nine, they will head to the Barracks; otherwise they will return to the castle to assemble them.
The troops are not always as discriminating as they should be about who they are attacking in a melee, which can result in your own troops killing each other, or another follower, or your horse, so large numbers can be counterproductive.
He commands battlemages who are of the Sorcerer class and have 20 points of Fortify Magicka.
Dame Avita Vesma
She commands the rangers, who are Hunters, and have Fortify Athletics, although there does not appear to be an actual bonus.
Brellin commands the coverts, Assassins with 10 points of Fortify Agility and 10 points of Fortify Sneak.
Sir Carodus Oholin
Sir Carodus's defenders are of the custom Knight of the Nine class and have 10 points of Resist Magic and 10 points of Shield.
His heavy infantry are Warriors with 10 points of Fortify Strength and 10 of Fortify Blade.
Sir Gukmir's skirmishers are Barbarians with 10 points of Fortify Speed and 10 of Fortify Athletics.
Lathon's archers are of the Archer class and have 10 points of Fortify Agility and 10 of Fortify Marksman.
Sir Thedret commands a mixture of defensive infantry and archers, equally split between the two as much as possible. The infantry are of the Knight of the Nine class and are identical to Sir Carodus's and the archers are Archers identical to Sir Lathon's.