Benjy~
09-18-2017

Special Purchase Bond(?

ReaD
10-11-2018

use in alchemy to get 100% success rate?

H.-Gazi
10-12-2018

They are used as ingridient for alchemy transmutation/transformation. Not all of them requires it, however, you will still lose them upon using them for the attempt unless you use wingless dragon book.

The book and the material will still disappear upon its success.

Guilder
12-13-2018

As Gazi says, it's used in certain Transmutation Alchemy recipes -- notably, the more impressive EX effect ones. The general formula goes (taken from Atromitos EX):

BASE ITEM + Orichalcum x1 + Check (10 million㌦) x5 + Special Purchase Bond x5

SPBs are very valuable, and of course, tend to be available from the cash shop only (or from players who've bought them from there to sell in-game).

Thanks to Gazi for confirming the general formula for me, which I'll leave here for posterity. If there are others, I figure they'll be listed here or on the UWO Wikia in time. Cheers.