Buy OSRS Wyrm bones
Wyrm bones are a Prayer training item in Old School RuneScape. They drop from Wyrms, which are level 97 monsters, and from Shadow Wyrms, which are level 259. Both drop the bones every time. Wyrm bones are members only. They are tradeable and noteable, but you cannot stack or equip them.
Burying a wyrm bone gives 50 Prayer experience. You can get more by offering the bones in other ways. A gilded altar with two burners lit gives 175 XP per bone. Grinding them into wyrm bonemeal for the Ectofuntus gives 200 XP. The Chaos Temple in the Wilderness gives 175 XP per offering with a 50 percent chance to keep the bone, so it averages 350 XP. You can also bless the bones and use blessed bone shards at the libation bowl for 210 XP, or 252 XP with a jug of blessed sunfire wine.
Burying a wyrm bone while wearing a dragonbone necklace restores 3 prayer points. The Bonecrusher from the Hard Diary gives 25 XP per bone. Wyrm bones have a buy limit of 7,500 every 4 hours, so you can stock up fast for Prayer training.