Geode Golem

Geode Golem's triggered ability triggers even if it's dealt lethal damage at the same time it deals combat damage to a player.

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.

If you cast a card “without paying its mana cost,” you can't choose to cast it for any alternative costs, such as bestow costs. You can, however, pay additional costs. If the card has any mandatory additional costs, such as the commander tax, those must be paid to cast the card.