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 every 0.25 seconds after not attacking for 2.5 seconds.
Active:Jax enters a defensive stance for up to 2 seconds, causing all basic attacks against him to miss. Jax also takes 25% reduced damage from all area of effectabilities.
At the end of the duration or if Counter Strike is reactivated, Jaxstuns all nearby enemies for 1 second and deals physical damage to them, increased by 20% for each attack dodged, up to a 100% increase.
It will also cause Muramana's bonus damage to trigger twice with a single attack.
Grandmaster's Might's bonus resistances are calculated on-cast and adjust dynamically.
There is a weird bug occuring with Grandmaster's Might's passive happening on turrets. When Jax basic attacks a turret 3 times (and only 3 times) and then quickly change target (within 2.5 seconds), his 3 next basic attacks will apply Grandmaster's Might's passive 2 times (on the first and third basic attack).