Since This is my first 'guide' and first day on the site, I didn't want to go into long detail about it. So here's the short version of talent choices:

This build is centered around the Executioner talent at level 16. I wanted to pick talents that provided the most up time for the talent to provide the +40% damage. Please know that until you reach level 16, the talents are better used to help secure kills for your teammates.

Level 1: The Shade talent. This helps Xul cover an area that he lacks and that's escape. It may not get him out, but it can provide the needed time t get to safety or help. Enemy heroes that are excellent at chasing down their targets, like Illidan and Lunara, can be deterred momentarily with this talent. I know the Shackler talent provides a 1 second slow when activated, but Xul's attack speed isn't that high so you'd only get 1-2 hits in at best.

Note: If the enemy team is heavy on spell casters, I recommend taking the Shackler talent instead.

Level 4: Death's Reach. This talent gives Xul a bit more range if you don't want to jump into an area and allows him to poke at the enemy. This also works with the level 14 talent Decrepify, this gives Xul a chance to close the distnce between him and his target.

Level 7: Rathma's Blessing. This was a tough decision and one that I recommend you think about before choosing. Each of these talents has their place and strengths. However I chose Rathma's Blessing for the healing. This allows Xul to remain in lane longer or recover after a chase.

Note: Obviously if the team i heavy on attack speed enemies, take weaken. This could mean the difference in a 1v1 fight.

Level 10: Skeletal Mages. I believe that this ability is far better than the poison Nova. Not only do the mages provide the slow needed in this build, but it is great in helping control an area. Similar to the Kael'thas Phoenix, these mages can be strategically placed in objective area to aid your team or be used to block of escape routes for your targets.

Level 13: Decrepify. This talents adds a slow to your increased range Spectral Scythe. This will allow you to close distance on targets that may be hard to catch. I've heard that Xul is an easy to kite enemy, but land this skill shot can get you close enough to land the prison and kill.

Level 16: Exectioner. The whole build is centered on this talent, however if you feel that your team can secure the kill without your damage input or you want to avoid 1v1 situations Then take the Amplify Damage talent. This helps not only you, but anyone else make quick work of the imprisoned enemy.

Level 20: Mortal Wound. The talent was chosen assuming the enemy team has a healer. It can be very frustrating if you spend a lot of time chasing a hero only to lose the kill due to the nearby support. If the enemy team has no healer, I recommend Bone Spear. This skill shot, similar to Abathur's spike, can deal considerable amounts of damage when paired with the slow.