This is a Celtic blackwork bookmark; it’s a free pattern from Needlework Tips and Techniques. It does have quarter stitches, but I worked it on 14 count aida anyway. I used three strands for the full and quarter cross stitches in the triangles, two strands for the cross-stitch border and the diagonals of the triangles, and one strand for everything else.
I used glow in the dark threads for it. The bulk of it is in DMC E940; the outline between the cross-stitch border and the actual design is an Artiste floss that I’m fairly sure I got on clearance at Hobby Lobby. The Artiste floss was a package with two colors on large cards/bobbins (one white, one green) and I used the green one; the texture of it was more like a DMC metallic than a standard floss. Both flosses were annoying to work with because the strands were two-ply and separated while I was working with them.