2023-02-04 : If a spell has {X} in its mana cost, you must choose 0 as the value of X when casting it without paying its mana cost.

2023-02-04 : If you cast a spell "without paying its mana cost," you can't choose to cast it for any alternative costs. If the card has any mandatory additional costs, those must be paid to cast the card.

2023-02-04 : If you wish to cast the card, you do so as part of the resolution of Synthesis Pod's ability. You can't wait to cast it later. Timing rules based on a card's type are ignored.

2023-02-04 : The spell you exiled as part of the cost to activate Synthesis Pod's ability will remain in exile.

2023-02-04 : To activate Synthesis Pod's ability, you must exile a spell you control on the stack (the only place spells exist).