
The Yeti Cool Brothers, Rocks and Scotch are famous for defeating Zoro in Punk Hazard. They are Yetis (and very, very Cool, as well as siblings: that's why they call them the Yeti Cool Brothers)
Rocks and Scotch = Rox D. Xebec reference?
Like Loki, they are much taller than normal Giants, being 4250 cm (139'5")[3]
Like Loki, they are introduced in a frozen wasteland.


(we got their actual faces in the One Piece 15th Anniversary Dive to Grand World Minibook)

Like Loki's subordinates in Elbaph's Underworld, one of them is wearing a gas mask (Scotch wears the mask, Rock is maskless)
We know Elbaph worships Nika; they should know about the Straw Hat. What are they wearing? Looks like Straw Hats to me
Loki is called a Demon: 666 is a Satanic/evil number. Chapter 666 is titled "Yeti Cool Brothers"
These guys were very powerful offensively, but weak defensively.
So, yeah: I think the Yeti Cool Brothers were Loki's subordinates.