Living Fireball (CR 4)

Medium Ooze
Alignment: Always neutral
Initiative: +1 (Dex)

AC: 13 (+1 Dex, +2 deflection), touch 11, flat-footed 12
Hit Dice: 5d10+5 (32 hp); DR: 10/magic
Fort +5, Ref +5, Will +5
Speed: 40 ft.
Space: 5 ft./5 ft.
Base Attack +3; Grapple +4
Attack: Slam +4 melee
Full Attack: Slam +4 melee
Damage: Slam 1d4+1 plus fireball
Special Attacks/Actions: Engulf, explode
Abilities: Str 13, Dex 12, Con 12, Int -, Wis 13, Cha 15
Special Qualities: ooze traits, SR 15
Feats: -
Skills: -
Advancement: 6-14 HD (Large); 15-20 HD (Huge)
Climate/Terrain: Any
Organization: Solitary
Treasure/Possessions: None

Source: Dragon #329

Engulf (Ex): A living fireball can flow around a Medium or smaller creature as a standard action. It cannot make a slam attack during a round in which it engulfs. A living fireball merely has to move over the opponents, affecting as many as it can cover. Opponents can make attacks of opportunity against the living fireball, but if they do so they are not entitled to a saving throw. Those who do not attempt attacks of opportunity must succeed on a DC 13 Reflex save or be engulfed; on a success they are pushed back or aside (opponent's choice) as the spell moves forward. Engulfed creatures take 5d6 points of fire damage (Reflex DC 13 half) and are considered to be grappled.

Explode (Su): Every time a living fireball strikes a target with its slam attack or engulfs a creature, it explodes in a blast that reproduces the effects of the fire ball spell. Creatures within 20 feet of a living fireball when it explodes take 5d6 points of fire damage (Reflex DC 14 half).

A living fireball attacks with single-minded intent. Making frequent use of its explode ability, living fireballs charge into battle and bathe their enemies in wave after wave of magical flame.