Some powerful giant kind spellcasters are capable of transcribing runes and giantish words of power on an otherwise mundane rock or boulder suitable for throwing by a giant. These runes and words of power trigger as the spell or spell effect transcribed, upon successfully hitting a target with the hurled rock. Any spell effect aoe is centered on the rock, where it hits its target.

This spellbook contains the following spells: slow, explosive runes, shatter, ice storm – only these can be transcribed. The attuned user of the spellbook consumes a spell slot of the appropriate level when ensorcelling or charging the rock, and otherwise preparation of the rock requires 500gp spent per level of the spell cast on it to prepare and finely chisel the runes, polish it etc.

This spellbook is made up of four heavy marble tablets, each weighing 100lb. When a spell is transcribed onto a rock, one of the tablets disappears, like a charge.