[Suzerain of Sheol]

That all sounds about right.

Gurthang is Turin's sword, means "Iron of Death," forged by Eol the Dark Elf (not like DnD dark elves, just an elf that never set foot in the Undying Lands, and hence was never infused by the Light of Aman). I believe the sword is forged from meteoric iron and is semi-sentient. I think it had a sister-blade as well, but its name eludes me.

Elu Thingol rules Doriath with his wife, Melian, a Maia, and yes, she upholds an interdiction around the entire realm.

The worst part about that story? Hurin eventually, inadvertently enacts both the Siege of Gondolin and the Ruin of Doriath after he gets free. The guy just can't get a break.