Elriel exists because Elain is feral for Azriel
(It’s in the books!)
“Azriel emerged from the sitting room, a glass of wine in hand and wings tucked back to reveal his fine, yet simple black jacket and pants. I felt, more than saw, my sister go still as he approached. Her throat bobbed.” - ACOFAS
“‘She made ballrooms into battlefields and plotted like any general. Like you two,’ she said, nodding to Cassian, and then, a bit more shyly, to Azriel. Azriel offered her a small smile that Elain quickly looked away from.” - ACOSF
‘I was just checking on dessert,’ Elain explained as they approached the doorway and Azriel. Nesta met the shadowsinger’s stare and he gave her a nod. Then his gaze shifted to Elain, and though it was utterly neutral, something charged went through it. Between them. Elain’s breath caught slightly, and she gave him a shallow nod of greeting before brushing past…” - ACOSF
“‘I should go,’ Elain said, but made no move to leave. ‘Yes,’ he said, his thumb sweeping in long strokes along the side of her throat. Her arousal drifted up to him, and his eyes nearly rolled back in his head at the sweet scent. He’d beg on his knees for a chance to taste it.” - ACOSF
