Thousand-Year Conundrum

Players can't cast creature spells.
At the beginning of each player's pre-combat main
phase, that player may put a creature with converted
mana cost 4 or less from their hand onto the battefield.
Sacrifice X creatures: Put a creature with converted
mana cost three times X or less from your hand to
the battlefield. X cannot be 0. Any player may
activate this ability but only any time they could cast
a sorcery.