Thanatos VII

From Memory Alpha, the free Star Trek reference

Thanatos VII is a Federation planet.

In 2370, a plasma conduit was manufactured on this planet using a new interphasic fusion process, which was later installed on the USS Enterprise-D at Starbase 84. However, this new process had attracted interphasic organisms, which later infested the ship's crew and made the Enterprise's warp core malfunction. (TNG: "Phantasms")