Roiling Horror

If the second triggered ability is countered, the card can't be cast. It remains exiled with no time counters on it, and it's no longer suspended.

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.

Due to a recent rules change to suspend, you are no longer required to cast the suspended card as the second triggered ability of suspend resolves. Instead, as the second triggered ability resolves, you may cast the card. Timing permissions based on the card's type are ignored. If you don't cast the card, it remains exiled with no time counters on it, and it's no longer suspended.

If this is suspended, then when the last time counter is removed from it, both its triggered ability and the "you may cast this spell" part of the suspend ability will trigger. They can be put on the stack in either order.

The mana value of a spell cast without paying its mana cost is determined by its mana cost, even though that cost wasn't paid.

You can exile a card in your hand using suspend any time you could cast that card. Consider its card type, any effects that modify when you could cast it (such as flash) and any other effects that stop you from casting it (such as from Meddling Mage's ability) to determine if and when you can do this. Whether you could actually complete all steps in casting the card is irrelevant. For example, you can exile a card with suspend that has no mana cost or that requires a target even if no legal targets are available at that time.

A creature cast using suspend will enter the battlefield with haste. It will have haste until another player gains control of it. (In some rare cases, another player may gain control of the creature spell itself. If this happens, the creature won't enter the battlefield with haste.)

Cards exiled with suspend are exiled face up.

If you cast a card "without paying its mana cost," such as with suspend, you can't choose to cast it for any alternative costs. You can, however, pay additional costs. If the card has any mandatory additional costs, you must pay those if you want to cast the card.

Exiling a card with suspend isn't casting that card. This action doesn't use the stack and can't be responded to.

If an effect refers to a "suspended card," that means a card that (1) has suspend, (2) is in exile, and (3) has one or more time counters on it.

You never choose an opponent, and the opponent that Roiling Horror looks at is never "locked in." Roiling Horror continuously looks at the life totals of all opponents and uses whichever value is the largest.

If your life total is less than or equal to the life total of the opponent with the most life, Roiling Horror's toughness is 0 or less. It will be put into its owner's graveyard as a state-based action.