I altered his powers considerably, though keeping the same theme I originally intended, this version basically makes him much less 'watery' in terms of powers, making him more 'solid' than originally imagined, though his body can still be manipulated in numerous ways, it takes longer and more energy to do so, and more accurately explains how he is capable of utilizing the energy in his core. Hopefully this set up will be far more acceptable. ^.^
Fire Elemental Core: His actual 'body' is a spherical object about the size of a basketball containing vast ammounts of energy and capable of producing immense heat when exposed. This core also can absorb various types of energy and heat from other sources, such as sun-light, fire, weaker energy weapons [stronger ones can't be compensated for properly.], and so on. When it absorbs too much energy to contain it will expand to properly hold the energy, and likewise when a lot of energy is 'released' the core will 'lose' mass.
Liquid Body Mass: His 'visible' body is made up of a black Liquid like substance, it behaves somewhat like melted rubber but bears noticeable magnetically responsive qualities. The normal state of his body is a semi solid rubber like feeling, it would be somewhat sticky, but would not respond completely as something made of water might. As such it can mitigate various heat and electrically based threats fairly easily, as well as physical threats, though sufficient levels of force and magnetic effects will still break through and explosives are highly likely to 'splash' him about.
He can use the energy contained in his core in a number of ways, a few examples below, but not completely limited to those listed, however more uses will need to be learned IC through practice and experience.
1. Controlled Exposure: Through manipulating the fluid making up his 'containment', he can expose the core within himself, and form a tunnel of sorts through which the energy will compress and be released, causing effects ranging from a simple blast of force and heat, to combusting and launching a gout of flame from the hole in question. The more exposed the core is within him the more energy that goes into the attack and the faster it is used up.
2. Electrical Release: Currently his most recent discovery and still being tested for how to use properly, but by exposing his core in a similar manner to number 1 and circulating the releasing energy within himself into a large enough collection he can cause it's release to bear enough energy in a single quick strike to release a lightning bolt. Doing so however takes a large ammount of energy and a mild charge up period.
3. Containment fluid Production: An important function of his core is it's ability to produce and control the containing liquid body mass that keeps his core from burning things around him. The larger the core, the greater the 'base fluid level' is, or more simplified, the larger he will appear unless purposely compacting himself due to the level of fluid needed to fully contain the heat he produces. He can reconstruct damage to his fluid body by expending energy to create more, as well as expending energy to forcibly create more to use for attacks and such.
4. Minor Magnetic Effect: Due to the current level of energy he contains this only affects things touching him, but his 'magnetic field' is used to shape and properly contain the fluid that makes his visible 'body', and can be used to attach metallic things to or within his body or to affect magnetically vulnerable things with touch. This is effect is easily over powered however, as well as causing him to be vulnerable to stronger magnetic forces, in the sense that it will forcibly destabilize and even tear apart the magnetically responsive fluid part of his body.