Overload exists on instants and sorceries, and is actually two static abilities. The first says that as you go to cast the spell, you may instead pay the overload cost. The second says that if you do that, you then replace all instances of the word “target” on the card with “each.”
- If don’t pay the overload cost, the spell has a target, and therefore can’t target anything with hexproof, shroud, or an appropriate protection ability. If you do pay the alternate cost, the spell has no targets, and can affect things with hexproof, shroud, or protection (depending on the effect).
- Overload is an alternative cost, but does not change the total mana value of the spell.
- Taxing and/or discount effects do affect the alternate cost of a spell.
- If there is an effect that lets you cast a spell without paying it mana cost, you cannot use that to cast an overloaded spell. You can still cast it that way un-overloaded.
Overload was a well-liked mechanic, and had some powerful spells featuring it. The biggest obstacle to its return is that it’s a little tricky to design – finding effects that work well with it and are balanced is already tricky, and it requires a pretty spell-heavy environment. It could see a return someday, but it will take some stars aligning.
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