There is a legal phrase called promissory estoppel, which essentially means that if your promise has serious repercussions for the other party and by not keeping it you caused some sort of harm (financial, in this casespoiler alert), youre liable for that harm and can be prosecuted
Lethal Scheme is by and large a free spell, and we know how powerful those can be
It doesn't target any player, even if the spell mastery ability applies
Ashnods Altar, Altar of Dementia, and the Eldrazi Monument give us three options for sacrificing creatures
Glin, Dwarf Emissary Lord of the Rings Glin, Dwarf Emissary is a very interesting Treasure-related commander, allowing us to sacrifice Treasures to goad creatures