The following rules were developed whilst playing 5th Edition Dungeons & Dragons, though work well in OSR play. The intention was to make weapon durability simple enough that it could be tracked easily, and would not ruin fun. I find it works to create tension, giving the players both an outlet for spending gold, and an incentive to loot equipment more often. Above all, I want my players to view their arms and armor as actual things which their characters are holding, rather than as attacks or defences.
Although a well-wrought weapon may survive decades in caring hands, poor use will wear a sword thin. Each time a 1 is rolled on an attack check, the weapon loses 1 point of durability, manifesting as a -1 modifier on future attack checks. When a PC suffers a critical attack, their armor degrades, belying -1 AC.
Equipment will degrade up to -3, but one more foul roll will final break the piece. The cost to repare is 25% the equipment's price, per level of degradation. Whenever a piece of equipment is taken from a fallen foe, the regeree ought to roll 1d10 to determine the condition: 1–4 is normal, 5–7 is -1, 8–9 is -2, and 0 is -3. Tracking enemy durability in the heat of combat may lead to truer verisimilitude, but is not necessary for game balance.
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