Overload

Overload is a keyword ability that was introduced in Return to Ravnica as the mechanic for the Izzet guild.

Description
Overload provides an alternate, usually more expensive, mana cost for a card which can be used when casting it, and upon doing it increases the whole effect of the card.

History
Overload was designed by Ken Nagle during the first Great Designer Search. After Return to Ravnica, Dragon's Maze added 2 cards, and it also reappeared in Commander 2015 and Modern Horizons, the latter used the keyword only in colors not used in priot sets. Mind Rake in the latter set was the first card with an overload cost that is less expensive than the mana cost, mainly due to how it can also affect the player who cast the spell as well.

Rulings

 * If you don't pay the overload cost of a spell, that spell will have a single target. If you pay the overload cost, the spell won't have any targets.
 * Because a spell with overload doesn't target when its overload cost is paid, it may affect permanents with hexproof or with protection from the appropriate color. For example, if you cast Blustersquall and pay its overload cost, creatures you don't control with protection from blue will be tapped.
 * Note that if the spell with overload is dealing damage, protection from that spell's color will still prevent that damage.
 * Overload doesn't change when you can cast the spell.
 * Casting a spell with overload doesn't change that spell's converted mana cost. You just pay the overload cost instead.
 * Effects that cause you to pay more or less for a spell will cause you to pay that much more or less while casting it for its overload cost, too.
 * If you are instructed to cast a spell with overload “without paying its mana cost,” you can't choose to pay its overload cost instead.