Thick-skinned

A thick-skinned monster is a monster that will only be dealt one damage when attacked by a bullwhip. Thick-skinned monsters have the flag M1_THICK_HIDE in the source code.

The following monsters are thick-skinned:
 * Gargoyles and winged gargoyles
 * All mimics
 * Mumaks, titanotheres, baluchitheriums, and mastodons
 * All dragons (including the Chromatic Dragon and Ixoth)
 * Earth elementals
 * All nagas
 * Xorns
 * Skeletons
 * Wood, clay, stone, glass and iron golems
 * Horned devils and barbed devils
 * Sharks
 * Crocodiles and salamanders