I was dueling the AI. I had Dark Contract with the Eternal Darkness with 2 "D/D" cards in my P-zones, and d'Arc. Then the AI activated The Monarchs Stormforth and tributed my d'Arc to Tribute Summon Vanity's Fiend.

Also, I Pendulum Summoned both D/D/D Armageddon & D/D Savant Copernicus from my Extra Deck but couldn't use the Pendulum effect of Dark Contract with the Grotesque Entity.