Arachnians

Arachnians are only seen in Serpent Isle in the lair of Aram-Dol, who created them by fusing the torsos of men with the bodies of giant spiders. They eat their prey alive and have a weakness to fire.

This terrifying creature has the full body, head and legs of the giant spider, with the torso, head and arms of a man growing from just behind its spider-head. Speculation abounds as to the origin of these horrible hybrids; some claim the mad servants of Chaos created them in one of their endless foolish experiments; others say it was the work of a long-dead lunatic mage. Regardless of how they came to be, the Arachnian is perhaps the deadliest of all foes at Serpent's Fang.

Trivia

 * It appears as though Arachnians were to be included in the cancelled Ultima X, although the shown picture is not specifically described as such. Link: Ultima X Arachnian?