Gossamer has one tattoo: a small spellwrought tattoo of find familiar linked to a lust imp that calls herself Moxie. It's on the right side of her body, ribs, just beneath the line of her breasts, and it's simply Moxie's True Name in Infernal. Every member of the Saints of the Eye has one, linked to a different variety of imp; they were gifts from Baator. (The wizard was a spy sent to keep an eye on the Demon Lords, and her middle-manager devil brought them to us as we prepared to heist our way through Menzoberranzan.)
She hasn't summoned Moxie since the end of the Rage, though. The last time they saw each other was at Gossamer's 'coronation' in the Argent Palace, when she fought her way free of Graz'zt. Moxie was disincorporated in the fight, and that was that. Gossamer never re-summoned her again when all was said and done.