For the reward from The Eyes of Glouphrie quest see Small crystal seed.
A Crystal seed is what is left over after a Crystal bow's or a Crystal shield's charges are used up. Seeds can be converted to a bow or shield by Ilfeen for a price. The price falls each time Ilfeen converts a seed to shield/bow. The minimum prices that Ilfeen will charge are 180,000 coins for bows and 150,000 coins for shields. Alternatively, bows and shields can be purchased new from Islwyn without needing a crystal seed.
One of the rewards for completion of the Roving Elves quest is a partially charged (2/10) crystal bow or crystal shield.
The only method of obtaining more crystal seeds outside of player transactions is through buying new crystal equipment at a minimum price of 750k ( Crystal Shield) and 900k ( Crystal Bow) and then using them till they decay into a seed.
Trivia
A player wielding a Crystal Seed in the weapon slot after a crystal bow has lost its charge.
- Sometimes when a crystal shield loses its charge, the seed is left in the shield slot. The same is possible with a crystal bow and the weapon slot.
- At a certain point in the game's history many people discovered that they could alch crystal bows for 540k and thus make enormous profit. This was later patched and crystal equipment is now unalchimizable.