Updated: Jan 26
The Voltron strategy has an inherent problem of only dealing damage to one opponent at a time. To address this problem the following creatures have no other utility but to allow Avacyn deal more damage.
Aurelia, the Warleader
Gisela, Blade of Goldnight
Kediss, Emberclaw Familiar
Kediss is a good low mana answer to this problem by making Avacyn deal damage to all opponents. Aurelia helps similarly by providing an additional combat phase, which can synergise with attack and combat damage triggers. Gisela is somewhat of a pet card, but justified by supporting the Voltron strategy and her damage reduction ability can be quite helpful too.