All 7 Combos with Terra, Herald of Hope

Terra, Herald of Hope + Aurelia, the Warleader + Karmic Guide + Ashnod's Altar

Infinite Mill: 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, Infinite colorless mana

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.