The Hydra was sculpted by Trish Morrison and the Sorceror probably by Aly Morrison as part of the mid 1990s Dark Elf release. The Hydra on its own was available in blisters at the US Games Day in 1999. The Sorceror appears in a picture in the mid nineties Dark Elf army book, but was never released. The howdah was also not released.
There are two variations on the front right leg as can be seen in the bottom picture.