Creatures on the Battlefield are permanents
Aegar, the Freezing Flame Alrund, God of the Cosmos Arni Brokenbrow Birgi, God of Storytelling Cosima, God of the Voyage Egon, God of Death Esika, God of the Tree Firja, Judge of Valor Fynn, the Fangbearer Hakka, Whispering Raven Halvar, God of Battle Harald, King of Skemfar Inga Rune-Eyes Jorn, God of Winter Kardur, Doomscourge Koll, the Forgemaster Kolvori, God of Kinship Koma, Cosmos Serpent Magda, Brazen Outlaw Maja, Bretagard Protector Moritte of the Frost Narfi, Betrayer King Orvar, the All-Form Reidane, God of the Worthy Sarulf, Realm Eater Sigrid, God-Favored Svella, Ice Shaper Tergrid, God of Fright Toralf, God of Fury Toski, Bearer of Secrets Valki, God of Lies Varragoth, Bloodsky Sire Vega, the Watcher Vorinclex, Monstrous Raider
Sothera, the Supervoid Sothera is just an updated Grave Pact that had a baby with Pestilence: a four-mana enchantment that gets rid of an opposing creature when one of yours dies and that stops sticking around once there are no creatures in play
While I guess you could try to flip it into a 3/4, and that might be the right line in some situations, I think there would be decks (at least in Standard) that would play the front side as a sorcery
No, if an effect like dredge replaces your draw, you can't use the miracle cost
On the other hand, once this turns into a full-fledged e-sport (I wonder what other highly competitive, tournament-friendly games are going to end up with new installments thanks to e-sports