It is actually possible to share placement number with another player, this is all based on MMR ratings
In other words, if a creature has flying, it can only be blocked by another creature with flying
Not only is it effective against opposing graveyard strategies, but it also lets you tuck cards from your own graveyard back into your library, making them accessible again with Green Suns Zenith , Knight of the Reliquary , or simply giving you another chance to cast them
Invasion of Ikoria instead gives you a huge dinosaur that allows your attacks to effectively ignore blockers when dealing damage
Sometimes, bringing back Aurelia herself plus one creature with Haste (from Hanweir Battlements, for example) is enough to close a game or remove a player
Sacrifice as an activation cost is a way to increase a spells cost without having it cost additional mana