Demonically Fused Fire Elemental* (CR 2)

Small Elemental (Fire)
Alignment: Always chaotic evil
Initiative: +7 (+3 Dex, +4 Improved Initiative); Senses: darkvision 60 ft., Listen +2, and Spot +3

AC: 18 (+1 size, +3 Dex, +3 natural, +1 dodge), touch 15, flat-footed 14
Hit Dice: 2d8+2 (11 hp)
Fort +1, Ref +6, Will +0
Speed: 50 ft.
Space: 5 ft./5 ft.
Base Attack +1; Grapple -1
Attack: Slam +5 melee
Full Attack: Slam +5 melee
Damage: Slam 1d4+2 and 1d4 fire
Special Attacks/Actions: Burn
Abilities: Str 14, Dex 17, Con 12, Int 8, Wis 11, Cha 13
Special Qualities: elemental traits, immunity to fire, cold resistance 5, haste, smite good, SR 4, vulnerability to cold
Feats: Dodge; Improved Initiative (b); Weapon Finesse
Skills: Listen +2 and Spot +3
Advancement: 3 HD (Small)
Climate/Terrain: Any land and underground
Organization: Solitary
Treasure/Possessions: None

Source: Dragon #285
Dragon Compendium Vol. 1

Burn (Ex): Those hit by a fire elemental's slam attack must succeed at a DC 12 Reflex save or catch fire. The flame burns for 1d4 rounds. A burning creature can take a move action to put out the flame.

Creatures hitting a fire elemental with natural weapons or unarmed attacks take fire damage as although hit by the elemental's attack, and also catch fire unless they succeed at a DC 12 Reflex save.

Haste (Su): The demonically fused elemental gains the effects of the haste spell.

Smite Good (Su): Once per day the demonically fused elemental can make an attack to deal +2 additional damage against a good foe. The creature must decide to use its smite power before its attack. A missed attack wastes that use of the smite good ability.

A demonic fire elemental takes joy in burning the creatures and objects of the Material Plane to ashes.

Fire Subtype

A creature with the fire subtype has immunity to fire. It has vulnerability to cold, which means it takes half again as much (+50%) damage as normal from cold, regardless of whether a saving throw is allowed, or if the save is a success or failure.