The only way to get a Kurask head is by killing Kurasks, which requires 70 Slayer. Players must then take the head to the Taxidermist in Canifis, who will stuff it for 6,000 coins. Once mounted, the head cannot be reclaimed. If players remove the mounted head, they will receive nothing back. Jagex has stated that this is because mounting the head rewards Slayer xp, and they did not want players to be able to train slayer by removing and remounting the kurask head.
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