Familiar

A Familiar is a creature that is the pet or companion of an individual and is bonded to that individual, such as by magic or mind control.

Advantages
A key trait of having a familiar is the significant power gain that both sides experience. This can be abilities being strengthened or gaining new uses, senses heightened, physical or psychic power improved, and even one side gaining powers the other side posseses. Both sides also heal more quickly, as one can draw on the energy of the other in order to speed up healing. A master and familiar can also easily read each others' thoughts, a valuable asset in combat.

Disadvantages
Two disadvantages that come from the minds of the two sides being so tightly linked are a significant loss of individuality as time passes as well as psychic attacks being able to target both through the mind of one. In addition to this, when one dies, that side still continues to draw on the energy of the other in order to heal- however it is impossible to simply heal the life back into a corpse in that fashion. What ends up happening, invariably, unless the dead individual is revived, is all the energy- including life energy- is drained from the living partner, eventually causing that partner's body systems to fail, often resulting in a heart attack. This takes an average of twelve hours depending on the manner of death, which side survived(familiars die more quickly), and whether or not the living partner was injured.

Bound by Magic
There are several spells at the disposal of any skilled mage that allow the binding of a familiar. Any one of these spells can be used on any animal, usually a smaller animal than the caster, though large creatures such as dragons have been known to be bound. These familiars are often used to strengthen the effectiveness of spells and can be considered the classic "pet" of the mage in question. The only requirement of binding a familir via magic is both sides must be aware of the result.

Mind Control
One of the more controversial methods of binding a familiar is to use a form of mind control such as necromancy or dracomancy, however contrary to the name, these familiars are willing creatures who can break their link with their master any time they like. They are also very often powerful creatures, sometimes more powerful than their masters, especially in the case of dracomancers where a dragon is bound. In order to bind a familiar via mind control, three conditions must be met:
 * The target must not be unwilling- they must offer no resistance. A truly unwilling target will resist, whether aware of it or not. Failure to meet this requirement while meeting the other two will result in creating a slave stripped of all free will, not a familiar.
 * The master must use their mind control at full force, without holding back or being distracted by anything else. Failure to meet this requirement will result in a normal binding, ie, the target will still retain its free will but be unable to resist orders, break the link on their own, and will not gain the benefits of a familiar, nor will the master.
 * The master must intend for the target to fully retain its free will. While this may seem contradictory to the second requirement, it is not only possible but vital to meet both requirements. Failure to meet this requirement will result in the target being stripped of all free will.

It is possible to bind a familiar in this fashion without the target actually being willing. If the target has lost all control of itself, there is technically no mind to control. While this prevents existing mind control from working if the target is under the influence when not berserk, it does not prevent it from being subjected to new mind control. As long as the target is not in its right mind, its brain will not recognize mind control and will therefore offer no resistance to it. Binding a familiar in this case is risky as once the target returns to its senses, it can easily break the link on its own and attack its master.

Failsafe Efficiency
And familiar bound by mind control may be released from any and all telepathic links simply by one "master" saying the words "obey no one but yourself" like any creature bound by mind control. It does not matter that a familiar still retains its free will.

Trivia

 * Any creature bound against its will, with the exception noted in the Mind Control section, cannot be a familiar.