At the beginning of your combat phase, Terra's first ability triggers, causing you to mill two cards.
Declare Terra and Aurelia as attackers.
Aurelia 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 twice by sacrificing Aurelia and Karmic Guide, adding {C}{C}{C}{C}.
Resolve the Terra ability, choosing to pay {2} to trigger its reflexive ability, returning Karmic Guide from your graveyard to the battlefield tapped.
When Karmic Guide enters the battlefield, it triggers, returning Aurelia from your graveyard to the battlefield. 
Repeat each combat phase.

Infinite LTB

Infinite ETB

Infinite sacrifice triggers

Infinite death triggers

Infinite self-mill

Infinite combat phases

Infinite untap of creatures you control

Infinite mana creatures you control can produce

Infinite combat damage

Terra, Herald of Hope

Aurelia, the Warleader

Ashnod's Altar

Karmic Guide

At the beginning of your combat phase, Terra's first ability triggers, causing you to mill two cards.
Declare Terra and Aurelia as attackers.
Aurelia 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 Aurelia, adding {C}{C}.
Resolve the Terra ability, choosing to pay {2} to trigger its reflexive ability, returning Aurelia from your graveyard to the battlefield tapped.
When Auriela enters the battlefield, Amulet of Vigor triggers, untapping Aurelia.
Repeat each combat phase.

Amulet of Vigor

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 {C}{C}.
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.
Repeat each combat phase.

Combos with "Terra, Herald of Hope"