those decks care more about the lost tempo than finding any specific spell
It at least kills things pretty efficiently at two mana, but the conditions it asks for make it much less powerful
Without going too deep in the top-down design, the Mosswood Dreadknight is the sets take on the Arthurian legend of the Green Knight who, after being decapitated by Sir Gawain, rides away for the two to meet a year later hence the card coming back from the dead after a time
Spell Mastery Some instants and sorceries in Magic Origins have spell mastery abilities
Four mana for a support piece that only triggers on creature death is a slow start, and outside of a dedicated Villain Commander deck built around Doctor Doom or Zemo, there are better options at this slot
People looking for the next Pokmon card create the next surge When products that have risen significantly in price appear, people looking for the next one always appear