It counters un-counterable spells, stops triggers as small as Mulldrifter and as big as Emrakul, the Promised End, and can prevent the cascade of value that a player might still reap even if their spell is countered
Casting a spell with overload doesn't change that spell's mana cost
Among these, only 220 have earned the coveted gem mint 10 grade, and 513 are in mint 9 condition
To determine the total cost of a spell, start with the mana cost or alternative cost you're paying, add any cost increases, then apply any cost reductions
If you're using Sword of Hearth and Home, you can also flicker your Knight for yet another land if someone else is ramping hard
Explore Explore is a cantrip/ramp spell