The same set weighs differently from one sealed box to the next, so there is no fixed heavy number only heavy relative to other packs in the same box
up to 3 could be Rare or Mythic Rare, along with 2 to 4 Uncommon cards in the pack
That changes if the bonus card they provide doesnt matter, in which case forcing your opponent to cast that card is pure tempo upside
This is a pretty handy floodgate against Evolution decks
Obosh, the Preypiercer Suggested Cut: Combustible Gearhulk The Lord of Pain, as well as other important damage dealers in this deck like Brash Taunter, Descent into Avernus, and Vial Smasher the Fierce, all happen to have odd mana values
That last borrows the special treatment from the recently released Unfinity set, applying them to four specific lands that see plenty of play in non-standard formats