While there are other options for Cleric commanders, most of them happen to be Clerics, but dont provide a payoff for what Clerics do
As her Revival Trance deck puts it, fill your graveyard and revive your fallen heroes. Put simply, Terra lets you return a creature from the graveyard to the battlefield at the price of 2 mana whenever she damages a player
While a little lackluster in stats, as is expected of the Puppy archetype, Patch does gain more lore as long as another Puppy is in play
And for seven mana, you can exile any permanent to then transform her into the Mothercrystal, doling out counters and making one of your creatures indestructible (a great way to protect your Destined Warrior)
an aggressive commander that draws cards seems useful, especially with a few cheap dragons like Changeling Outcast and Clarion Conqueror to maximize the cards drawn off the second ability
An ability that triggers "whenever you cast a historic spell" doesn't trigger if a historic card is put onto the battlefield without being cast