Rishkar's Expertise

If you control no creatures with power greater than 0 as Rishkar's Expertise resolves, you draw no cards, but you may cast a card with mana value 5 or less from your hand without paying its mana cost.

If you cast a card "without paying its mana cost," you can't choose to cast it for any alternative costs, such as emerge costs. You can, however, pay additional costs. If the card has any mandatory additional costs, such as that of Cathartic Reunion, you must pay those to cast the card.

Any triggered abilities that trigger while performing the Expertise spell's first effect won't be put onto the stack until after you're done casting your free spell. They're put onto the stack at the same time as any abilities that triggered while casting that spell regardless of the order in which those abilities triggered.

While you're casting your free spell, the Expertise spell is still on the stack. It will be put into its owner's graveyard after the free spell is cast. The free spell can't target the Expertise card in your graveyard. It can target the Expertise spell on the stack, but the Expertise spell will become an illegal target before the free spell resolves.

The greatest power among creatures you control is determined as Rishkar's Expertise resolves.

If the card has {X} in its mana cost, you must choose 0 as the value of X when casting it without paying its mana cost.