invoker

One who calls upon (a person, especially a god) for help, assistance or guidance.

One who appeals for validation to a (notably cited) authority.

One who conjures up spirits with incantations.

Someone who induces as an inevitable consequence.

One who solicits, petitions for, appeals to a favorable attitude.

Computing, Engineering, Mathematics, Natural sciences, Physical sciences, Sciences That which causes a program or subroutine to execute.