The Brief: E, X, and XTC are individual abbreviations and slang terms for the drug, ecstasy.

DEEP DIVE
Someone looking for ecstasy, or a plug who’s trappin’, might refer to ecstasy as E, X, or XTC. Ecstasy-use is especially popular amongst Millennials and Gen Zers in the nightclub and rave scene.
My mom told me when we're were moving from our old house she found her old ecstasy… In baggie spelled XTC
— Eloise Kay (@eloise_kay) May 2, 2014
I had no idea people nicknamed ecstasy, "xtc". I'm so fascinated. #easilyamused
— Marina Rose Joyce (@MarinaJoyce7) June 16, 2013