Paraelemental Plane of Magma
The Paraelemental Plane of Magma is the Inner Plane formed between the Elemental Planes of Earth and Fire. The Paraplane of Magma is a veritable sea of molten rock, too solid for creatures of fire, and too scorching for creatures of earth. Native creatures include magma paraelementals and magma mephits.
In the early days of 1st Edition Advanced Dungeons & Dragons, the Paraelemental Plane of Heat took the place of the Paraplane of Magma.