Blackened Iron Bastard Sword
 

Is this item currently in the game or did this get introduced in a later patch?

Thanks

Yes, I can confirm that it drops from a Goblin Knight on the second floor of Runnyeye. If you check the wiki, there's a map of the second floor that shows a room marked "5", which is where he can spawn.

It is in the game. Achievement for the discovery of the sword was awarded. It happened as Nagafen was already dead.

Doesn't it also drop in Befallen?

No.
Bone Bladed Claymore is the befallen 2hs

Yes it should be in game. It is Blackened Alloy that comes out later when Runnyeye is changed to Runnyeye 2.0