This build is for most active pudge players. these items allows you to constantly roam and kill without ever going back to base; therefore influencing your opponent to play more scared. so waht if you miss the hook, soul ring gets you enough mana for the next one. This active mobile gank build will UnNerve ANY opponent!!!
EDIT: this build was created long time ago. these days you are able to buy a blink dagger, but dont be a fool and always buy blink first. sometimes forcestaff is just way better as a first item. you are a roam/support after all so ocasionaly you are going to need it more.