Little is known of the tome guardian’s life

Habitat/Society: Little is known of the tome guardian’s life on the Elemental Plane of Fire, but interactions observed on the Prime Material Plane indicate that they are on reasonably good terms with most other creatures of flame. Only fire elementals that meet the parameters discussed here are summoned as tome guardians, so it is unknown if they have a weaker form (such as the lesser elemental summoned by a Daltim’s fiery protector spell) or develop into something else later.

A mage summons the tome guardian by casting an ensnarement (sending or demand can work if the guardian’s name is known; they do have personal names), and compels it to service by the use of a binding spell. The object to be guarded must be visible to the mage, who indicates it (by pointing and speaking) to the guardian. Tome guardians do not mind protecting an object, for unknown reasons of their own, and unless otherwise attacked are not hostile.
The guardian envelops, and appears to merge with, the object it has been bound to, becoming invisible. The object radiates a faint dweomer, and infravision detects the presence of the guardian – but the creature cannot be telepathically contacted or in any way coerced, tricked, or forced to leave its object except as described previously (through the use of a dispel magic). A guardian can guard only one physical object – and if the object is composed of readily separable parts, only one part (for example, a sword or its scabbard, not both). The guarded object must be small (of less than four cubic feet volume), and nonliving. Usually magical tomes of lore are so guarded, hence the guardian’s name.
An individual can summon only one tome guardian per 24 hours. Normally, only one guardian can be bound to any object, though unsubstantiated reports suggest the presence of one or more within a single item is possible. If so, the method for binding more than one tome guardian to a single object is a generally unknown process, available only through the most obscure of arcane lore.
Guardians that are summoned to the Prime Material Plane but not successfully bound to an object, or who have been driven forth from the object they were guarding, assume what is known as their “free form”, and remain on the Prime Material Plane for 2d20 turns before “dwindling away”, returning to their own plane by natural means. They are not under any being’s control during this time, and attack any creature who attacks (or attempts to control) them. Otherwise, they are attracted to large fires, of natural origin (such as volcanoes and forest fire) or manmade (like bonfires, forges, or even isolated campfires).
A tome guardian can be bound to a magical item, serving as a protector, or perhaps even being trained to release a fireburst if its guarded item is used in an attack (for example, if a tome guardian is bound to a sword, then that sword could be used to deliver three firebursts per day, in addition to any other powers it has). If attached to a magical item that produces flame or electricity (such as a ring of shocking grasp), the tome guardian absorbs such energies and prevents their function. However, at the DM’s discretion, such energies might be used to enhance the tome guardian’s fireburst ability.
Symbols and glyphs cast upon a guarded object do not affect the guardian and function normally against others. Note that fiery or electrical protective spells such as explosive runes and fire trap can be cast upon a tome guarded by a guardian, but the creature absorbs the spell energy as it is being cast, so that the spell’s protection does not exist (and the guardian gains, for a day, hit points equal to the maximum damage these spells would have dealt).
Tome guardians can coexist peacefully with guardian yugoloths, guardian familiars, homunculi, and the like, as well as with other creatures of elemental fire. If a guardian is brought into the presence of a xeg-yi, they attack each other at once. Otherwise, the tome guardian is peaceful and solitary, at least on the Prime Material Plane.

Ecology: Ecology: Tome guardians might collect treasures on their home plane, but on the Prime Material Plane, a tome guardian is never found with more treasure than the item it guards and whatever might be lying nearby. They collect nothing, and they do not pursue prey of any kind. Sages who know about these creatures generally agree that they must feed on warmth, fire, and perhaps even light, and that they may even take nourishment from the heat of bodies they cause to burn.

If killed, a tome guardian’s essence dissipates in a wave of heat and a dusting of ash. The ash has proven a viable ingredient for oil of fiery burning and smoke powder, and would presumably serve well in other fire-related potions or magical items. The heat released by the death of a tome guardian has been suggested as a means to temper a ring of fire resistance. The creature’s fireburst might also be useful in igniting the flame powers of certain items, like a flame tongue sword; however, touching an item to the tome guardian in hopes of this is a dangerous proposition, because the fireburst attack still affects the wielder of the item.
It is also possible, as hinted at before, to bind a tome guardian to an item specifically to make that item magical. In fact, a small number of fireburst daggers, daggers with bound tome guardians, are known to exist. For the first three attacks each day with such an item, roll an attack roll against AC 10, adjusted only by Dexterity and any magical bonuses. If the attack is successful, the tome guardian propels a fireburst into the victim. The fireburst is not used if the item does not hit. Once the item has hit three times, it cannot use fireburst again until the next day, but it can still be used as a normal item of its type.