Is split second just another way of saying “this card can’t be countered”? To me, it has no other qualities? Once this card is removed from the stack opponents are then free to cast spells. So I’m guessing we just treat this as a can’t be countered spell despite its fancy naming convention or can it do more than what I’m perceiving?
Split Second has uses other than making a spell uncounterable.
As a simple example, say you cast Sudden Shock; targeting a creature with only 2 toughness. If not for Split Second, your opponent could save the creature by casting a spell any spell that does any of the following:
- Increases the creature’s toughness
- Gives the creature Hexproof
- Gives the creature protection from your spell
- Regenerates the creature
- Prevents the damage
Several ways he could save his creature. But due to Split Second, he can’t respond at all; and the creature will almost certainly die.
Similarly if you cast Sudden Shock targeting your opponent who has 2 life. He can’t cast anything that will increase his own life.
There are all sorts of ways other than countering a spell that you might want to respond to a spell. Split Second prevents all of them.
While Split Second is generally more powerful than “cannot be countered” due to the reasons stated; in some cases “cannot be countered” will work better, such as if there’s a triggered ability that counters spells, such as the emblem from Jace, Unraveler of Secrets.
No, split second refers to how a spell can be responded to.
For instance, Krosan Grip has split second, but with a successful Counterbalance flip, can be countered. Split second doesn't itself make the spell uncounterable, it just prevents the majority of ways the spell would be countered from happening (casting a counterspell, etc.)
From the comprehensive rules
702.60. Split Second
702.60a Split second is a static ability that functions only while the spell with split second is on the stack. “Split second” means “As long as this spell is on the stack, players can’t cast other spells or activate abilities that aren’t mana abilities.”
702.60b Players may activate mana abilities and take special actions while a spell with split second is on the stack. Triggered abilities trigger and are put on the stack as normal while a spell with split second is on the stack.
@Gendolkari's answer is a great answer for why "Split Second" is more powerful than "Can't be countered". I'd like to add a supplement for all of the reasons why it is weaker.
Here's how to counter a split second spell:
Triggered abilities that counter spells, such as the emblem from Jace, Unraveler of Secrets, Erayo's Essence, Chalice of the Void, Kira, Great Glass-Spinner, Counterbalance, Chancellor of the Annex, or Decree of Silence.
Triggered abilities that give you other triggered abilities that let let you counter spells, such as Hunting Grounds or Lurking Predators putting a Mystic Snake or a Draining Whelk onto the battlefield.
Unmorphing a creature (which is a special action that is allowed while a split second card is on the stack) that counters the spell, such as Voidmage Apprentice, Stratus Dancer, or Silumgar Spell-Eater
Split Second can be used to ensure you do things while holding priority when casting spells. Ex. You cast Damnation, holding priority you cast Sudden Spoiling (Split Second). This would leave no one able to respond except through triggered abilities and special actions IF they have any.
There are a few jank ways to utilize Split Second, most forget about Players holding priority when responding or using the stack, so it helps to bring that up as well.