Translate it as "I have writer's block when it comes to thinking about her for some odd reason and I'm asking for help." I reserve the right to veto or modify any suggestions made.
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It's a Sidhe-only feat. Basically, at some point in their life, a Sidhe can develop an innate, special power that is expressed through their hands. There's many things that it can be - for example, the previous Mab of the Unseelie Court was called the "Queen of Air and Darkness" because those were her Hands of Power. Generally speaking, a Sidhe will only have one Hand that is also their dominant hand, and it relies on touch. A second one CAN be developed, and the first Hand can be a ranged power, but it's usually reserved for the High Lords.
Known examples include:
The former Mab of the Unseelie - Hand of Air, Hand of Darkness
Ross - Hand of Blood, Hand of Bone
Ross's mom - Hand of Glamour, Hand of Death
Callista, Spring's Heir - Hand of Strength, Hand of Darkness
Anya, Maeve of Winter - Hand of Healing, Hand of Flame
Akasha, Mab of Winter - Hand of Change, Hand of Magic
Titania of Summer - Hand of Light, Hand of Water
These are generally
quite powerful. They have several different tiers - someone who just got their Hand isn't going to be on the same level as someone who had it for centuries.
Upon receiving it, a kill
must be made to keep it, or else it goes away. Opportunity knocks very rarely.
EDIT: I'm sure you'd like more detail, so:
Blood: Rhoslyn's right Hand of Power grants him several abilities: a ranged touch attack (untyped magical, about 2' wide from the center of his hand, shaped roughly cone-like in its forward projection), a limited degree of blood sorcery, increases the power potency of his own blood, and allows him to gain more power from blood than the average faerie. The ranged touch attack causes cuts to appear on or within his target - within five meters, these wounds are akin to paper cuts. Within three meters, this power causes damage akin to a shallow knife wound, and contact will begin to cause damage to the muscles and tendons underneath like a deep knife wound. However, the nature of this attack (reflecting one's own power back upon themselves, in essence) means that those who do not use any supernatural powers will at best get what looks like claw wounds if Rhoslyn's right hand touches their bare skin. On the other hand, a pure mage would have the area Rhoslyn touched shredded. This attack deals "permanent" damage - passive regeneration does not affect wounds inflicted by this attack, nor does shapeshifting cause the injuries to fill in.
The "blood sorcery" does not have limits as to what he CAN do with it - eg, he can make it sticky, make it explode, burn, form simple weapons, etc - but the actual "power level" of whatever ability he chooses to manifest will generally not exceed the power of an "instant" ability, cannot exceed the total power of a post's worth of charging, solely applies to his own blood (except for blood-based healing, due to a long time of practice and constant exposure to certain artifacts), cannot take multiple properties at the same time, and once the choice is made as to how the blood is charged, it cannot be changed.
Bone: Rhoslyn's left Hand of Power allows him to control the bones (or exoskeletons) of organisms he comes in contact with, as well as his own skeletal structure. This can be used to heal and reset broken bones, but he prefers to make them weakened, explode, fracture, grow "claws" and the like. This power does not instantly effect his target, nor can it affect the entire body of his target at once - Rhoslyn must sustain contact for a short time before he can begin to use this ability. The longer the contact is sustained, the greater control he gains and the larger his area of control gets. When applied to himself, the ability is an instant, and can be applied to any part of his body he sees fit.
Strength - When triggered, Callista gains increased strength that surpasses the preternatural strength all fey already have. This enables her to leap tremendous distances, lift massive weights (think, TONS of weight) and strike opponents with terrifying force. She is capable of increasing the strength of targets through touching them (therefore explaining how she can lift such enormous weights without, y'know, being crushed through the ground.) Right hand, although using it on herself applies to her entire body.
Darkness: Callista's recently manifested Hand of Darkness allows her to call and manipulate darkness. At the moment, she is capable of forming shapes of darkness and forcing it into a physical manifestation, although it doesn't last very long. Left hand.
This power gives Aņa power over flames. It can be used to conjure forth mystical flames, aggravate flames, cause them to burn without oxygen/fuel, or extinguish them. Further, she can sense flames, and even remove or add heat/light from said flames not under her control. There is no upper limit or lower limit - if it can be burned, Aņa can and will burn it. If it can't be burned, most of the time, she can set it on fire anyway - meaning yes, she can set water on fire if she feels like it. Or set fire on fire. Needless to say, fire and heat damage do not effect her as a requisite secondary power. Right hand.
Hand of Healing: With this hand of power, Aņa can heal herself as well as others. However, she cannot bring life back if it is not there or give back limbs as if the injured were a starfish. This is a very powerful hand but unfortunately it has its downsides. Often, she will experience mild symptoms of the wound she healed (e.g. healing a blow to the head, she would experience mild to severe migraines depending on the severity of the wound. A deep cut, she may have a scratch on her arm that throbs a little, etc). The wounded will feel a warmth when they are healed and in rare times a healing light will seem to permeate from her hands. Left hand.