There's a bit of legend concerning demons (in the "actual" mythology) that assigns "seals" to all of the major demons. These seals are used when summoning them (as part of the binding) as well as are considered their signatures.

I decided Gilrandree should have a seal. As part of a forthcoming commission, laken-steeljaw did a design of one, which I ended up revising slightly and cleaning up.

Thus, here's Gilrandree's Seal. (For other examples, just google search for "Demon Seal." If you like graphical design, you may find them interesting to look at.)