The Nightmare Chunk traps Pi'llo's inside, and they cannot be freed until Mario breaks it.
History[]
Before Antasma was banished into the Dream World by the Pi'illo's, Antasma shattered the Dark Stone, and broken pieces became Nightmare Chunks, and if fallen onto a Pi'illo, where it would trap them inside. The Pi'illo's would be trapped for many years until discovered by Mario.
Gallery[]
Mario and Luigi encountering a Nightmare Chunk