New Shyvana Passive Idea

Passive:

SHORT VERSION: Shyvana gains stacks of Berserk on each attack; doubled against champions. At 8 stacks, her next attack will deal bonus damage and give her Movement and attack speed for 3 seconds. (10 - 7 second cooldown)

MATH VERSION: Every basic attack Shyvana gains a stack of Berserk; she gains 2 versus champions. Stacks last 10 seconds and the duration is increased by 3 seconds upon gaining a new stack. (e.g. if the stacks are 5 seconds into expiring and you attack, the timer will be reduced to 2 seconds. Just a way to refresh the duration without completely resetting it.) At 8 stacks her next basic attack will deal (40 / 50 / 60 / 70% AP) bonus magic damage, and Shyvana will gain 20 / 30 / 40 / 50% movement and attack speed for 3 seconds, which will start to decay after 1 second. This ability has a 10 / 9 / 8 / 7 second cooldown, starting when she receives the buff (affected by CDR). Shyvana cannot gain stacks while this is on cooldown.

[Levels 1 / 6 / 11 / 16]

Let me know how it is!