Panicked screeching

Way back when he first learned what chimerism was, Mixtus had a very upsetting dream that his (apparently evil) twin's cells began taking him over. For years, he'd forgotten about that nightmare. But, getting too close to an Umbrum right after seeing a bunch of ponies become possessed has apparently brought that dream back, in the form of an extremely vivid hallucination. Yet another horror remake no one asked for!