The Hydra itself was sold 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.
Sculptor:
Aly & Trish Morrison
Painter:
Finlay Light
Source:
Orclord
Released:
1999