I am looking for a word to describe someone who has your fate in their hands. It might be an archetypal name of some sort, as well as a freshly coined word. It would be perfect to have a tinge of irony in it, although it is not necessary.
One possibility is master. Among the several definitions, Collins lists
a person who has complete control of a situation
This obviously has heavy historical connotations, especially in cultures that have allowed slavery.
A somewhat more archaic term is overlord
One in a position of supremacy or domination over others. American Heritage
string-puller: A person who is in control of events or other people’s actions.
possibly Caiaphas -
in the rigged trial section of the article you find the following snippets:-
Caiaphas took on the usually incompatible roles of chief judge and prosecuting lawyer.
which suggests he has your fate in his hands.
the irony is that:-
The trial went wrong for Caiaphas. He needed to prove that Jesus had threatened to destroy the Temple, which would have been both treason and an offence against God. But the witnesses couldn't agree on what Jesus had said. So that charge failed.
but maybe you should also consider
in the section political implications
Caiaphas' legal position was to establish that Jesus was guilty not only of blasphemy but of an act of sedition and prompted Roman execution.
In the Arts section:-
To Dante he is synonymous with hypocrisy.
but there is also:-
He is portrayed pulling Pontius Pilate's strings by trying to influence him into passing the death sentence against Jeshua in The Master and Margarita by Bulgakov.