Koschei the deathless is a Fremennik warrior that players must fight during The Fremennik Trials quest, in order to complete Thorvald the Warrior's test of bravery and win his vote. The player must defeat Koschei three times without dying; although they are told they must defeat him to win, defeating him three times is considered enough to win, as the test is of bravery, not strength.

Koschei's combat level is not shown; however, he will get progressively stronger and his attacks faster each time he is defeated. His max hits are 3 in his first form, 5 in his second, and 7 in his third. Although the fourth form is difficult, with 255 Hitpoints, it is not impossible to defeat him; if he is defeated, the player will be rewarded with a Fremennik blade.

Players can talk to Brundt the Chieftain about Koschei's history. when u go down u cant bring weapons or armor cause it be consider to be cheated since the Thorvald the Warrior doesnt allow them and he will check on the person before he or she can go down there. he wont know if its treasure clue scroll chest for some reason.