Juren, Combat Weaver

At the beginning of your upkeep, if you control less than three Runes, create a Rune artifact token with "Sacrifice this artifact: Add one mana of any color to your mana pool. Spend this
mana only to cast an instant or sorcery spell."
Sacrifice a Rune: Choose one - Juren gets +3/+3 and gains trample until end of turn; counter target spell or ability; or you gain 4 life and draw
a card. Choose each mode only once
per turn.