This is true even if you pay an additional cost while casting a spell "without paying its mana cost." If the legendary spell you cast this way is copied, the copy can be countered
Cast two spells in a turn to take advantage of the new Flurry ability or play some solitaire and cast as many as you want in a turn to take advantage of Prowess
There's one more thing to discuss: It looks like we're getting a transmission from someone
Burnished Hart, for example, costs only three
Unlike Cyclonic Rift, it only bounces creatures and it's symmetrical, but it's significantly cheaper to cast being only five mana instead of seven, and notably it's another spell that can be cast at instant speed
Uytkownicy ceni platformy, ktre pozwalaj pynnie przechodzi od rejestracji do gry, oferuj przejrzyste zasady nagrd oraz zapewniaj intuicyjne narzdzia do kontroli budetu