You have the ability to summon a Servant from the Throne of Heroes via a ritual, you will gain three command seals once the ritual completes. You can choose which Servant will be summoned. If you exhaust all three command seals or the servant is slain, you can perform another ritual to re-summon another Servant. When picked multiple times, this power allows you to summon multiple Servants at the same time, each servant has its own set of command seals.