The Shibboleth was a mutated Corpser. A large land-based monster under the control of the Locust Horde, it served as the personal mount of General Karn.
Shibboleth was a unique creature employed by Locust General Karn as his personal mount in battle. Shibboleth was unique in that it had claws very close to that of an infant Corpser (one of which is a mechanical prosthetic) and with the ability to launch Nemacysts.

The Shibboleth was very big. Giant. >:3 (they don't speak)