Spell unbind

In the game: help unbind

Take a prism apart into its runes.

You can unbind prisms, causing them to collapse into the primary prism and all the runes that were added.

Hold the prism that you want unbound in your hands and type 'SPELL UNBIND'. The prism and any runes added prior will appear in your inventory.

The game also finds it under: unbind, spell unbind.