Amorphous
Version 0.33: This article may not be up to date for the latest stable release of Crawl.
Amorphous monsters do not have a definite shape or form. They include jellies and liquid elementals like water elementals and elemental wellsprings. They are immune to throwing nets, webs, bolas, and constriction. Also, they take less damage from Shatter if not petrified.
History
In 0.33, the Amorphous flag was added.