Eternal Dragon practically lives in the graveyard as it is and Twilight Shepherd expects to go there at any minute
The modality of an artifact/enchantment removal effect or a bite spell would make this very powerful, but it can also be a tutor, one thats also flexible
I excluded the Vow cycle of Vow of Malice, Vow of Torment, and Vow of Duty, but theyre in the maybe pile, so if you like them, give them a shot and let me know how it turns out
it's an expensive removal spell, but it does stuff we want - either kills an Insect or puts itself in the 'yard as it comes in, building up our 'yard for when we cast our Commander
It is also very cool that this card says legendary spell, which means all planeswalkers and other types of legendaries as well