I - Rules
(see JITD, p. 15, 16, 23)
After inflicting at least 1 damage (before applying the effects of armor) to a figure with a Stun attack, place a stun token next to the figure. A figure can have more than one stun token next to it at a time. Named monsters cannot be stunned, and master monsters suffer reduced penalties when stunned.
Stun tokens indicate that a figure is confused or dazed. On that figure's next turn (or the next time the overlord activates the figure, in the case of monsters), the stun token is discarded.
If the figure was a normal monster, its action immediately ends - it can do nothing else until the overlord's next turn.
If the figure was a master monster, it may either move up to its speed or attack once.
If the figure was a hero, the hero does not receive a full action this turn. Instead, the hero may only move a number of spaces up to his speed or make one attack or place one order. A stunned hero cannot use any ability that requires advancing, running, battling, or readying (except for placing a hero order).
A figure may have more than one stun token on it at once: Only one stun token is removed each turn, so the figure will remain stunned for multiple rounds.
II - References
Heroes with the Stun ability: none.
Items granting the Stun ability: Binding Light, Flute of Repose, Pacify, Petrify, Word of Vaal.