黒いガングニール is a Weiß Schwarz card from 戦姫絶唱シンフォギアG SG/W27-076. Compare listings from Singapore Weiß Schwarz sellers on CardJio, then jio them on WhatsApp.
All your 《武器》 Characters, during that turn, get +1500 Power.
This card was printed in Japanese only; the English text above is an unofficial community translation.