Lost Honour is a side quest in 
Kuttenberg. You will encounter Sir Jezhek of Holohlavy, a man who lost his horse and armor in a wager gone wrong, and it is up to Henry to decide whether to help him through noble combat or stealthy thievery.
How to Start Lost Honour
This quest is initiated via a random encounter in the Kuttenberg region. While traveling the road between 
Miskowitz and Horschan, keep an eye out for a "Polite Armed Man" at the crossroads in the forest.
The encounter looks like this. Simply fast travel between Horschan and Miskowitz:
Jezhek will initially attempt to ambush you, though he isn't particularly good at it. You can avoid a fight by passing a Speech or Charisma check or by immediately surrendering.
If a fight does break out, ensure you stop attacking as soon as he surrenders.
Speak to Jezhek to learn that he lost his equipment to a soldier named Zavish of Garbow at Sigismund's Camp after losing a bet. Agree to help him to begin the quest.
Finding Zavish of Garbow
Make your way to Sigismund's Camp. If you don't have the access yet, you can tell the guards you are there on behalf of Jezhek of Holohlavy to gain free roam of the camp.
Zavish is typically found near his tent, located on the northern side of the fence running through the center of the camp, opposite the field chapel. You will see his coat of arms, a black eagle and three white stars, on a shield nearby.
Challenge Zavish to a Duel
Before speaking to him, it is highly recommended to wear your best clothes and drink some alcohol or use Mintha Perfume to boost your Charisma. If you fail these checks, your only remaining option will be to steal the gear.
To get the gear back through noble means, you must challenge Zavish to a duel, or steal them.
Honorable Path: Winning the Duel
The duel consists of three rounds with different weapon types. You must provide your own gear, which can be purchased from the camp armorer (west side) and blacksmith (east side).
To start, you need any longsword, any polearm and any one-handed weapon plus a shield. Once you have them all, return to Zavish and prepare for a fight.
To earn the Master of Masters achievement, you must win all three rounds in a row. It is wise to spend a Saviour Schnapps before initiating the tournament.
Round 1: Polearms
This is widely considered the hardest round. Polearms have a basic moveset and do not allow for master strikes.
Keep your distance and look for openings. Pushing Zavish into a corner can help, then repeat attack from the bottom angle for repeated stabbing.
Between every round, Zavish will leave the fighting ring and go heal. You can skip time for about 30 minutes until he comes back.
Round 2: One-Handed Weapon and Shield
Focus on parrying and master strikes. If using a mace, target his head. If using a shortsword, aim for his right side to avoid his shield.
Round 3: Longswords
Zavish is a master with the longsword, so do not get overconfident.
Rely on perfect blocks and master strikes. If you have already reforged Radzig Kobyla's sword, this fight can be ended very quickly with high stats and waiting for master strike opportunity.
After winning, Zavish will direct you to the items in his tent.
Stealth Path
If you lack the combat skills or the persuasion levels to duel Zavish, you can choose to steal the items.
Wait until nightfall and sneak into Zavish's green tent. Pick the lock on the chest (Hard) to find Jezhek's armor.
Also grab the Brigandine sitting on the ground next to the chest.
Then, go to the stables near the western exit from the camp and find Gringolet, the horse with the yellow caparison.
Once you mount the horse, the guards will likely be alerted, so ride out of the camp immediately.
Returning the Gear
Once you have the armor and the horse, travel to the Wagoners' Inn located on the main road to Kuttenberg and south of Pschitoky.
Ride Gringolet into the central yard of the inn. The quest objective should update once you are in the correct spot.
Speak to Jezhek inside the inn. You can either tell him the truth or lie to keep the gear for yourself. His gear is among the best in the game, especially the chestplate, gloves and plate pauldrons (shoulders).
Rewards
If you won the duel and returned the gear, Jezhek rewards you with 500 Groschen, the Lord of Holohlavy heater shield, and Jezhek's spurs (which have a very high Charisma stat).
If you stole the gear and returned it, the rewards are similar but Jezhek will be less impressed.
If you keep the gear and lie, you gain some of the best-in-slot items in the game, including Jezhek's Brigandine and his Gloves, which are superior to Milanese gauntlets. However, you will receive less Groschen and no unique shield.
This finishes the Lost Honour side quest in Kingdom Come: Deliverance 2.
Lost Honour FAQ
How do I start Lost Honour?
Random Jezhek encounter on the road between Miskowitz and Horschan. Fast travel until he appears.
Where is Zavish?
Sigismund's camp, north side of the central fence near the black eagle shield, opposite the field chapel.
How do I get Master of Masters?
Win all three duel rounds in one run. Use Saviour Schnapps before you start.
Which duel round is hardest?
Polearms (round 1). Corner Zavish and stab from the low angle. Skip ~30 minutes between rounds while he heals.
What are the best rewards?
Return gear after winning the duel: 500 Groschen, Holohlavy shield, and high-Charisma spurs. Keeping gear trades gold for top armor.