Fortify Familiar

Tome and Blood: A Guidebook to Wizards and Sorcerers (TB)Updated Supplementals (3.0)

Fortify Familiar is a D&D 3.5 spell (Universal) from TB. On class lists for Sorcerer (Level 4), Wizard (Level 4), Abjurer Variant (Level 4), and others. Range or area: Touch; Saving throw: None (harmless); Duration: 1 hour/level; Casting time: 1 standard action.

School
Universal
Casting Time
1 standard action
Components
V, S
Range
Touch
Target
The caster's familiar
Duration
1 hour/level
Saving Throw
None (harmless)
Spell Resistance
Yes

You make your familiar tougher.
While the spell lasts, it gains a +2 enhancement modifier to natural armor and has a 25% chance to avoid extra damage from sneak attacks or critical hits (though the attack still deals normal damage).
The familiar also receives 2d8 temporary hit points.