Snakes

Snakes rely on stealth. The normal adventurer won't notice them, until it is too late. The bite of a snake is very poisonous, and usually ends deadly. Physically however, Snakes are no challenge for even the weakest adventurer.

Snakes can be found either near swamps, in deserts or in dungeons.

Notable examples
Nate the Snake in the ruins of Magincia in Ultima IV. Nate gives The Stranger hints where to search for the rune of Humility and the Black Stone, before attacking, and dying in the process.