invoker

Noun

 * 1) One who calls upon (a person, especially a god) for help, assistance or guidance.
 * An invoker of God's mercy
 * 1) One who appeals for validation to a (notably cited) authority.
 * 2) One who conjures up spirits with incantations.
 * 3) Someone who induces as an inevitable consequence.
 * 4) One who solicits, petitions for, appeals to a favorable attitude.
 * 5)  That which causes a program or subroutine to execute.