Hey, this is my first build, so don't be to harsh on me :)
I'll shortly explain the choices I made in this build.
Spells
Ignite: I use this spell mostly on champions with alot of health. I open with a Tormented Soil and a Dark Binding. After that I use ignite and just start autoattacking till they are down (if done right this should do it).
Flash: This skill is nice if you need to catch up on other champs to shoot your Dark Binding at them. But flash also offers some great survival. With Rod of Ages you have alot of health for a caster. If they try to gank you, it's no problem, you can take some hits before you flash away. If they run after you, you can just trow a Dark Binding at them, or even a Tormented Soil as they always tempt to try and dodge it, wich gives you a lead. Flash saved my life a dozen of times.

Skills:
I always go for Dark Binding at the start, if you co�¶rdinate things well with your team you can almost assure a first blood (unless they flash of ghost sometimes). It always payed off for me.
Beside for the skill order above go with this prio order (for endgame specialy):
Soul Shackles > Tormented Soil > Dark Bindning > Black Shield

Items:
I'm not going to explain every item seperately, I'll do it global.
With these items you gain a nice bunch of health, but also an immense amount of mana (wich gets converted into AP). I never have to recall due to low mana mid-and-end game. I only have to recall to refill my health (after a battle).
Beside some survival and laning capabillities, you also get a nice amount of AP.
Just a little note: I chose Lich Bane because of it's passive. Alot of times after I used al my skills (Tormented Soil, Dark Binding, (Soul Shackle), (Ignite) I end up doing some autoattacks to finish it off, and well, Lich Bane helps as they tend to escape sometimes due to cooldowns.

Overal I think this build offers some survival aswell as the power to harras.
If you got questions / comments, leave them below :)