You’re a wizard! Or, at least, some of your champions are.
So you may not be a real master of the mystic arts, but here in Runeterra, spell casting is for everyone. There are a few different types of spells that correspond to when they can be played: burst, focus, fast, and slow.
Burst spells can be played any time and cannot be countered or responded to by any enemy spells. This means you can play as many as you’d like (until you run out of mana) as long as you have initiative. They're indicated by a sparkle icon on the left side of the spell and will say BURST in the expanded view.
Previously, you could only end a round after your opponent has fully passed without taking an action. From patch 3.6 onwards, if you pass after playing only a Burst or Focus spell, your opponent may end the round!
Focus spells work similarly to burst spells in that they resolve as soon as you play them and you can play as many of them as you'd like as long as you have the mana for it. The main difference is that focus spells can't be cast during combat or as a response to a spell.
As mentioned when going over burst spells, if you pass after playing only a Burst or Focus spell, your opponent may end the round. So don't forget to play other cards that may help you win before you end your turn!
Fast spells can be played during combat and in response to another fast or slow spell. Once both players have passed without adding an additional spell to the sequence, they will resolve in order of left to right.
Playing a fast spell will give your opponent the opportunity to respond, so be mindful of the times you use them (and keep your enemy's remaining mana in mind). Fast spells are indicated by a winged-shoe icon on the left side of the spell and say FAST in the expanded view.
Slow spells are, well...slow! But what they lack in speed, they often make up for in power. These spells can only be played when you have initiative, which means slow spells are unable to resolve during combat or in response to fast spells. They can be countered or responded to with fast or burst spells, so keep your enemy's remaining mana in mind when playing!
Slow spells are indicated by a purple clock on the left side of the spell and say SLOW in the expanded view.