Hunter's Mercy as my super-free standard.
Free move to Q20
Rapid Shot Full Attack
First Shot (If hit, Sern crit)
(1d20+13)[17]
(1d8+3)[7]+
(1d6+11)[13]
(1d8+14)[15]
(1d8+14)[22]
I use my special bow property to deny his dex to this attack cause I truly don't trust my luck. Since no specified action was tied to it in the description, I assume free action?
EDIT: Just realized that he's flatfooted anyway, disregard. Also...no crit, Sern quit
Second
(1d20+13)[23]
(1d8+3)[5]+
(1d6+11)[14]
Third (Haste granted)
(1d20+13)[25]
(1d8+3)[10]+
(1d6+11)[12]
Final
(1d20+10)[25]
(1d8+3)[7]+
(1d6+11)[15]