When someone is dropped into a Cube of Arcane, it is called a Cube Drop. This is usually done with very dangerous foes where there is a chance that if their body is found they might be resurrected. Dropping someone in also traps their psyche in the Cube, preventing them from moving on to a Soul Gathering System or from benefiting from a Soul Storage Depot.
The first recorded instance of dropping a prisoner into it happened in the Dawn Era when Ares "accidentally" dropped Cari'phis into Bal-Kriav's Cube. Belras Foroderch researches say that the unnatural blue-ice of Ice Cap and the volatile landscape of Gludragh came about because even though Cari'phis's body was annihilated, her psyche lives on.