To get Yorscalp gear you need to transform the Gaebolg gear.

Talk to Blacksmith Sansan at (mbase_in 230, 125).

You need for every piece of gear:

200x Wigner Merchant Guild Voucher (1001618)

10x Shape of Fallen Serpent (1001834)

50x Symbol of Curse (1001835)

200x Spirit of Yorscalp (1001836)