At the beginning of your combat phase, Terra's first ability triggers, causing you to mill two cards.
Declare Terra and Fear of Missing Out as attackers.
Fear of Missing Out triggers, causing you to untap all other creatures you control and to get an additional combat phase after this one.
Deal combat damage to an opponent using Terra, triggering its second ability.
Holding priority, activate Ashnod's Altar by sacrificing Fear of Missing Out, adding CC.
Resolve the Terra ability, choosing to pay 2 to trigger its reflexive ability, returning Fear of Missing Out from your graveyard to the battlefield tapped.
When Fear of Missing Out enters the battlefield, its first ability and Amulet of Vigor trigger.
Resolve the Fear of Missing Out trigger, causing you to rummage.
Resolve the Amulet of Vigor trigger, untapping Fear of Missing Out.