Islwyn Cadarn is the grandson of Queen Glarial and King Baxtorian and is a member of the Cadarn Clan. Upon completion of Roving Elves, he will sell players new Crystal equipment without the need of crystal seeds. He will sell players a new crystal bow for 900,000 coins or a new Crystal ward for 750,000 coins. The "new" bow or shield can be traded until it is used once. He used to be rather hostile towards humans, but one human adventurer's aid in the consecration of his grandparents' tomb changed this. Baxtorian informs the player during The Light Within quest that Eirlys is Islwyn's mother and Baxtorian's own daughter. After the quest he will give you the letter from Eluned if you let her live.
Islwyn can be found travelling with Eluned teleporting between the magic trees outside Lletya and the clearing north-east of Tyras Camp. One can find him by taking a charter boat to port Tyras, running north, going through a dense forest obstacle, then slightly east and south across a stick trap to reach the clearing or by teleporting to the Tirannwn lodestone, running north-east, through the obstacle, and then run south. After The Light Within Islwyn will replace Eluned in the Ithell Clan district of Prifddinas, recharging crystal seeds for players in her stead.
If assuming he and Eluned move every five minutes, and taking into account that he lights a fire each time, one will find that Islwyn has lit approximately 985,000 fires since his release date 3,860 days ago. Assuming he used normal logs, which give 40 firemaking experience each, he would have accumulated at least 40 million firemaking experience, which would equal level 110 firemaking. Also, assuming he cuts down a regular tree for each log at 25 woodcutting experience each, he will have gained almost 25 million woodcutting experience, which is equal to level 106 woodcutting.