[quote=@IncredibleBee] Yeah but the grail's a magical genie wish granting device as it is, so I'd say it could pull out some spare prana. May also be that an especially wily Heroic Spirit managed to force itself into the Grail War, perhaps forcibly sucking mana out of Fuyuki's ley lines. [/quote] It's just a mundane ritual on a huge scale. If you take away the scale then there's not much there. It's impossible for there to be enough prana to summon a Servant; if there was it would lead to a gaping plothole that I won't allow. You could take the Solomon clause of "I summoned myself because I'm just that good", sure, but a Heroic Spirit at that level is far too broken for me to allow. Besides, the Second Owner's now the true owner of the land, opposed to the greenhorn she was in the 50s. She wouldn't let someone jack her leylines nowadays. [quote=@Sodium] We can always pull the leeching prana from the lives of those in the city card. [/quote] I don't mean for maintenance, I mean for summoning. The Grail needs to touch the Throne, copy the data, shove it into a Spiritual Core and consequently give it form, bind it to an anchor (Master), and help maintain it. It doesn't have the leftover prana to do that.