The "Canker" side quest in Kingdom Come: Deliverance 2 is accessible early and requires completing "The Jaunt" beforehand. This quest offers a mace and Groschen, making it worthwhile. Here's how to complete it:

Initiating the "Canker" Quest:

Speak to Gules in Semine. This is easily done during Lord Semine and Agnes' wedding, while he's imbibing. Alternatively, find him on patrol in Semine. Inquire about his former bandit gang and offer assistance in eliminating them. Canker is the first target.

Locating and Eliminating Canker:

The quest marker will appear on your map, north of Nebakov Mill. Be wary of ambushes along the path; employ stealth, combat, or flight as needed. Canker's camp is nestled in the mountains, easily missed due to a narrow passage. Prepare for combat before entering, as several bandits will be present. While some bandits might flee, ensure you eliminate most, including Canker (who won't run).

Quest Completion:

After defeating Canker and the bandits, loot his body. The Light Mace is required, but feel free to take other items. Return to Gules to finish the quest.

A full in-game day must pass before the next quest, "Handsome Charlie," involving Gules' remaining bandits, becomes available. Speak with Gules again after this time elapses.