If the player does, they draw a card
It also draws you cards, which makes it easier to consistently play humans to trigger owyns ability
I guess the idea here is he's saving (reviving) some people and consuming (sacrificing) others, to indicate his anti-hero nature
Like so, in the same turn, you can use Mega Dragonite ex 's ability and attack again to deal 330 damage
If the total mana value of historic permanents you control changes while activating mana abilities (probably because you sacrificed one or more historic permanents), the cost to cast Excalibur remains what you previously determined
It also can continue copying creatures, gaining their power, toughness, and abilities every turn