As Foretold (WOT 68)

Enchantment • Mana cost: {2}{U} • Wilds of Eldraine: Enchanting Tales • Rare

At the beginning of your upkeep, put a time counter on this enchantment.
Once each turn, you may pay {0} rather than pay the mana cost for a spell you cast with mana value X or less, where X is the number of time counters on this enchantment.

Illustrated by Yuichi Murakami.