Declare Fear of Missing Out as an attacker, triggering its ability, causing you to untap it and to get an additional combat phase after this one.
Deal combat damage to an opponent using Fear of Missing Out, triggering Impostor Syndrome, creating a token copy of Fear of Missing Out that isn't legendary.
When the Fear of Missing Out token enters, it triggers, causing you to rummage
During your next combat phase, declare Fear of Missing Out and the Fear of Missing Out token as attackers.
The Fear of Missing Out token triggers, causing you to untap the nontoken Fear of Missing Out and to get an additional combat phase after this one.
Repeat from step 2.
This clever combo uses Rising of the Day to grant your team haste, allowing Fear of Missing Out to attack immediately and trigger its delirium ability for extra combat phases. As it connects with your opponent, Impostor Syndrome steps in to flood the board with non-legendary token copies of the creature. Every time one of these copies arrives, it triggers its own entry ability to rummage through your library while refreshing your attackers for endless, cascading combat steps.