(intransitive) to enter

to come into force, to come into effect

(intransitive) to throw one's hat in the ring, to enter the lists, to enter the running, to enter the fray, to enter the arena

to come into play / to step in

(theater) to come on (to appear on a stage) / (figuratively) to enter the picture, to enter the scene, to come on the scene

to take one's vows, to take orders (to enter a religious order, a religious community)

to go into action

to take up one's post, to start one's new job; to take office

(figuratively) to come into account, to enter the equation, to enter the picture, to count for something

(figuratively) to play someone's game, to play along with someone, to go along with someone, to get dragged into someone's game