I was MC’ing Monsterhearts for an all star crew, and the Infernal and the Witch had sex on an altar in the creepy apple orchard. She took her sympathetic token from him (his pentagram necklace) and the Infernal’s dark power gained swapped a string from him to her. Then the dark power offered them each an XP to sacrifice the teen they had in the trunk of the car on the altar.
And they gladly took it up on that count, the Witch even adding insult to injury, Withering the kid on his way to the altar.
They both then leveled up and both took the “rest of the spells” option from their playbooks.
The whole thing really made me appreciate the beautiful symmetry between those playbooks. The Witch powers her hexes through taking strings, the Infernal through giving them away. The Witch’s darkest self is about having too much power and the Infernal’s DS is about having his credit extended beyond his ability to pay.