This creature appears as a shimmering and wavering sphere of translucent gray energy with small motes of light winking in and out of existence along its spherical form.
A negative energy elemental that is killed explodes in a flash of swirling negative energy that affects all within the area (the radius for its death throes ability is the same as the radius for its negative energy aura). Living creatures within the area take 1d8 points of negative energy damage per two HD of the elemental. Negative energy based creatures and undead gain hit points equal to the amount of damage the death throes would have otherwise dealt. (The rules for temporary hit points and doubling hit points as detailed under the elemental's negative energy apply here.) A successful Reflex DC (save DC same as the elemental's negative energy save DC) reduces the damage by half.
A negative energy elemental infuses a target hit by its slam attack with negative energy. This deals extra damage to a living target (as listed in the statistics block) but heals undead (and other negative energy based creatures) by the same amount. Undead (and other negative energy based creatures) can be healed above their normal hit point total, gaining extra hit points as temporary hit points. These temporary hit points disappear 1 minute later. Creatures healed to twice their normal hit points (that is, a creature whose hit points are effectively doubled) must succeed on a Fortitude save or explode in a burst of negative energy. The save DC is Constitution-based. See the table below for each negative energy elemental's save DC.
Negative energy (such as an inflict spell or negative energy channeling) can heal negative energy elementals.
A negative energy elemental radiates an aura of pure negative energy around it. (See the table for the area each elemental affects.)
Within a negative energy elemental's aura, class abilities that use negative energy, such as negative energy channeling or the Command Undead feat, function as if the user were 2 levels higher. Additionally, spells and spell-like abilities that use negative energy are maximized (as if the Maximize Spell metamagic feat had been used on them, but the spells don't require higher-level slots). Spells and spell-like abilities that are already maximized are unaffected by this benefit. This aura does not affect the negative energy channeling ability of the negative energy elemental using it, and its effects do not stack with those of other negative energy elementals.