I have been planning on buying 
for a while now, and I was wondering what some good builds were for him and how to play as him. I know that he has 2 different forms. Shadow Assassin for burst and Darkin for taking down bruisers/tanks. I also want to get him because I only am able to play as 2 junglers right now, those being 
and 
.
Shadow assassin is a standard assassin build. All enchantments are good but I prefer 
or 
, for either chase down or warding, both of which are really good for assassins.
You don't HAVE to build 
on him, and sometimes it might be a better idea to rush straight to your lethality item, those being 
. Both are good and have their pros and cons. If you need raw damage to eliminte a fed adc for example, go duskblade. However, with the ghostblade movespeed active and passive you can get some INSANE map mobility and amazing flanks.
After those two items there are a few options.
is a bit of a tankier version, while if you wanna go full dmg you can get 
and 
instead.
After that, its whatever you may feel is needed. 
is really good against peeling champions like 
.
Is always good for a bit more waveclear and burst with teh active. 
and 
are defensive options if those are needed.
For Darkin, its pretty much the opposite. I like going for a heavy hp/ad build, like
and hten whatever boots you may need. You hit 30% cdr, which is really good since Darkinn Kayn has super good base values and you become a fantastic frontline and/or diver, which ever one u need.
is a seriusly underrated item. People think its the tank item, but its really not, its more like a . IT only gives 600 hp at max build, which isn't hat much and the active gives it dmg to rival off-tank items.
With darkin its important to remember, you're not a dmg dealer, you're a tank first and foremost
imo the red side (rhaast?) is way better for the team in most scenarios. The knockup alone makes him well worth it. just build like a bruiser from there
