The spell made a selected object completely immune to fire, such that it could not be burned by any means and remained always cool when touched. It had to be a solid object, and its volume in cubic feet was directly proportional to the caster's level of power.
Furthermore, if Daltim's proof against fire was placed upon something that could be worn, then that item provided the same immunity to the wearer. This was provided it offered sufficient coverage to block a flame, such as a cloak or suit of armor. A wearer became immune to any natural fire, and was better able to resist magical flame.
In addition to the usual verbal and somatic components, the spell required an ink concocted from the blood of a red dragon and a crushed ruby valued at 5000 gold pieces. Prior to casting, protective runes were brushed onto the item to be protected, and these faded away when the spell was cast.
The spell was developed by the Halruaan mage Daltim Flamefist sometime in the mid–14th century DR. He included it in his spellbook Daltim's Tome of Fire, which he lost in Tethyr in the 1360s DR. It remained a unique spell at the time.