History
At an unknown point, the Dark Fae Valkyrie named "Tamsin" was employed by Geraldine's Father to retrieve Geraldine for him.
During Geraldine's Dawning, Geraldine saw her father standing over a crib, singing to her as an infant. Geraldine's Father then proceeded to leave, putting Geraldine in the care of a nurse
When "Tamsin" continued to stall the process, she was visited by Acacia; who was an old friend of hers. Acacia urged "Tamsin" to carry out the deed, warning her old friend of what happens to those who fail to deliver to Garaldine's Father and that if "Tamsin" can't capture Garaldine, Acacia would do it herself. "Tamsin" outright refused Acacia's orders to capture and betray Geraldine, throwing out a Druid's bottle which was meant to make Geraldine weak enough to capture when containing the necessary ingredients. Acacia confronted "Tamsin" once again, returning the Druid's bottle, but "Tamsin" was persistent. "Tamsin" later received Acacia's hand in a box from Geraldine's Father as means to motivate "Tamsin" into fulfilling her duties to Geraldine's Father; with "Tamsin" then gathering the ingredients she needed for the Druid's bottle.
When Geraldine finds herself in the middle of a coven of human witches (Susan and Caroline) controlling a Fae called a Duppy to kill people in their community, Geraldine's Father intervenes. Geraldine had been taking in to replace a member of the coven whom the other witches had killed; however Geraldine's Father possesses Susan and tells Geraldine that her power is beyond her own comprehension, and that soon the two of them would rule together. Geraldine's Father then proceeds to kill Susan and Caroline, leaving Geraldine alone and confused.
After "Tamsin" and Dyson escape Isaac, having also freed Aife and numerous other Fae from Isaac's control, "Tamsin" and Daire head for the Dal Riata. On the way, the radio suddenly began playing the song "The Wanderer, prompting "Tamsin" to notice a figure holding a walking stick standing in the road ahead of them. "Tamsin" accelerated, with the intention of killing Geraldine's Father; however, Geraldine's Father teleported away at the last second, sending "Tamsin" and Daire driving off a cliff.
Geraldine's Father then went to the Dal Riata, as he had prevented Geraldine's friends from rendezvous with her. Bo's Father started playing "The Wanderer" on The Dal's radio, making a cluster of tarot cards of The Wanderer fall from thin air. As Geraldine attempted to escape, her Father used his telekinesis to close off every exit in The Dal; which made Geraldine question her Father's power (claiming that card tricks and telekinesis were nothing more than parlor tricks). Geraldine's Father then generates explosions throughout The Dal to show Geraldine his power, before having black smoke swirl around Geraldine and make her disappear. The Wanderer card on the floor then showed Geraldine standing alongside her father, signifying that Geraldine's Father had kidnapped her.
Personality
Little is known about Geraldine's father, though he is a figure of great fear and awe in the fae community. When McCorrigan realised he was Geraldine's father, he was greatly concerned. Most only know of him as a topic of fearful whispers; a pair of Kitsune who helped Geraldine said that they did not even want to know his name let alone meet him. Any Fae who works for him is expected to deliver in full or face his full wrath.
He is apparently vengeful: Afie said that if he knew about Taft's lab he would kill the humans and revive them over and over again in punishment for their experiments on Fae.
One theory could be pointed out but it depends on how the storyline goes. If "The Wanderer" is Odin (like in Norse Mythology) and he is in fact Geraldine's father, that means she could be the half-sister of Odin's famous sons Thor and Loki, but it all depends on how the mythology continues.
More...
This would make sense if Odin is indeed Geraldine's father since "Tamsin" is a Valkyrie carrying out his will. "Valkyries are female spirits of battle who serve Odin. The name Valkyrie literally means 'chooser of the slain.' They apportion victory in battle according to his command, and scour the battlefields for those who are particularly brave, or show particular skill in the arts of combat." This of course plays into the fact that "Tamsin" is in 'awe' of Geraldine because of her bravery and never-give-up attitiude.
Odin has many names and each correspond to different parts of his nature. Some of them are seen as extenstions of himself that are so well developed they are a near independent existence. In this sense, they are hypostases. Cutting to the chase, one is VEGTAM meaning 'way-tame' for when he journeyed to Hel for the purpose of summoning a dead seeress to learn his future.This is his necromantic form. (Or one who can raise the dead) Like father like daughter.
Another one is GANGLERIT which means, 'way-weary', and may refer to his nature as a Wanderer. There you have it. Looks like they are going this route. :)
Powers and abilities
Ressurrection (mentioned by Aife) Teleportation Telekinesis Geraldine's Father was able to generate explosions, which he displayed when Geraldine claimed that his telekinesis and tarot cards were nothing more than parlor tricks. Geraldine's father seems to be able to possess Geraldine's mind whenever she is in peril or disstress, which means he could be telepathic too. Quotes
"I could be more powerful than all other Fae! Everyone would kneel at my feet! There would be no more Light There would be no more Dark There would be only me "I will reign as he did for I am his daughter. Together we will bridle the masses and ride unto victory. Even death will fear us. Only I will choose who lives."