Generally speaking, skinning is considered as the most horrible action, even if it is made to all monsters. All of the monsters can be skinned in Agon after they are killed. After skinning a monster, a player can get a lot of resources which can be used in various forms of crafting or enchanting. Moreover, reagents can be acquired for casting a spell.
A player needs a skinning knife to skin a monster. Firstly walk up to the grave of a slain monster, secondly unsheathe the skinning knife, and finally left click while aiming at the grave.