Jax gains 3.5% - 11% (based on level) bonus attack speed for 2.5 seconds every time he lands a basic attack, stacking up to 8 times for a maximum of 28% - 88% (based on level) bonus attack speed. Stacks fall off one at a time.
At the end of the duration or if Counter Strike is activated again, Jaxstuns all nearby enemies for 1 second and deals them physical damage, increased by 20% for each attack dodged, up to a maximum of 100%.
Grandmaster's Might has no cast time and does not interrupt Jax's previous orders.
Despite being an on-hit effect, Grandmaster's Might's damage will trigger spell effects as a single-target spell, including spell vamp, Rylai's slow and will cause Muramana's bonus damage to trigger twice with one autoattack.
Although the bonus damage cannot affect structures, hits against them will still stack the counter, resulting in Jax repeatedly triggering the loud sound effect after three strikes.
The bonus armor and magic resistance is calculated when the ability is cast. Further changes to Jax's attack damage and ability power will not cause the bonus stats to dynamically adjust.