Definition of invokers:
(n) :
(computing) That which causes a program or subroutine to execute.
(n) :
One who calls upon (a person, especially a god) for help, assistance or guidance.
(n) :
One who appeals for validation to a (notably cited) authority.
(n) :
One who solicits, petitions for, appeals to a favorable attitude.
(n) :
One who conjures up spirits with incantations.
(n) :
Someone who induces as an inevitable consequence.