Damge return is a mechanic that allows character to reflect the damage caused by attacker. Unlike other games, the mechanic of damage return in solo knight is quite simple, character can only reflect the damage directly hit by attacker, rather than other types of attacks such as negatives, buffs, physical status, elemental effects, etc.
Many of our players are concerned about how the damage return is calculated in game, the first thing you need to know is that it is a hit effect, which means that it will only be triggered when the character is hit. In other words, it's not exactly the same as the amount of the damage the attacker dealt to character, but rather the damage that the character is actually taken. They are different concepts because you need to add defense properties into calculation, if an attacker takes 0 damages to you, the damage return won't be triggered though there is a buff on your head.
Similarly to the parry, Spiked Mail is the core equipment of a damage return based build, and since damage return operates in the form of buff, most buff-related runes can be inserted into Spiked Mail to increase its effect and duration. Besides, there are a number of options related to damage return in the passive tree and random attributes.

Damage return works in a form of buff in Solo Knight. When damage return is enabled, you can see a small icon at the top of the character's head.

The buff icon of damage return