While we don't have to mulligan until we find an engine piece, these are the cards that make the deck powerful, so a medium hand without a Sram or Spiritdancer is often worth mulliganing, especially with London mulligans making it hard to have a truly unplayable six-card hand, in the hopes of finding a Kor Spiritdancer or Sram, Senior Edificer
Turn #9 During your untap step before you untap, Old Fogey phases in
Eladamri is a solid pickup for Elves decks, like most pushed Elves these days
Playing an enchantment that probably doesnt impact the board the turn it comes down risks a big tempo loss, but the payoffs dont get much better than this
It can be fire damage, lightning damage, or poison damage
Neheb, the Eternal piggybacks on the life loss by providing mana to cast more spells