Korlessa, Scale Singer — ruling 1

You can look at the top card of your library whenever you want (with one restriction; see below), even if you don't have priority. This action doesn't use the stack. Knowing what that card is becomes part of the information you have access to, just like you can look at the cards in your hand.

Korlessa, Scale Singer — ruling 2

If the top card of your library changes while you're casting a spell, playing a land, or activating an ability, you can't look at the new top card until you finish doing so. This means that if you cast a spell from the top of your library, you can't look at the next one until you're done paying for that spell.

Korlessa, Scale Singer — ruling 3

Korlessa doesn't change when you can cast Dragon spells. Normally, this means during your main phase when the stack is empty, although flash may change this.

Korlessa, Scale Singer — ruling 4

You'll still pay all costs for the spell, including additional costs. You may also pay alternative costs if any are available.

Korlessa, Scale Singer — ruling 5

The top card of your library isn't in your hand, so you can't take other actions that would normally be allowed from your hand, such as discarding it due to an effect or activating a cycling ability.

Korlessa, Scale Singer : règles, fonctionnement et interactions (MTG)

Korlessa, Scale Singer is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

You may look at the top card of your library any time. You may cast Dragon spells from the top of your library.

How it works : Korlessa, Scale Singer

Original English text — Wizards of the Coast / Scryfall

#1June 10, 2022· Wizards of the Coast
You can look at the top card of your library whenever you want (with one restriction; see below), even if you don't have priority. This action doesn't use the stack. Knowing what that card is becomes part of the information you have access to, just like you can look at the cards in your hand.
No other card is named in this ruling.
#2June 10, 2022· Wizards of the Coast
If the top card of your library changes while you're casting a spell, playing a land, or activating an ability, you can't look at the new top card until you finish doing so. This means that if you cast a spell from the top of your library, you can't look at the next one until you're done paying for that spell.
No other card is named in this ruling.
#3June 10, 2022· Wizards of the Coast
Korlessa doesn't change when you can cast Dragon spells. Normally, this means during your main phase when the stack is empty, although flash may change this.
No other card is named in this ruling.
#4June 10, 2022· Wizards of the Coast
You'll still pay all costs for the spell, including additional costs. You may also pay alternative costs if any are available.
No other card is named in this ruling.
#5June 10, 2022· Wizards of the Coast
The top card of your library isn't in your hand, so you can't take other actions that would normally be allowed from your hand, such as discarding it due to an effect or activating a cycling ability.
No other card is named in this ruling.