Scourge of the Skyclaves

[Artaud]

In Commander multiplayer game Scourge of the Skyclaves will have negative values of P/T when it enters the battlefield usually (unless kicked). Am I right these values are the same when Scourge "rots" in graveyard and can account as discount for cards like Nethroi, Apex of Death?

[Kenjiblade]

Scourge of the Skyclaves has a characteristic-defining ability that determines its power and toughness. Such an ability applies at all times in all zones, including the graveyard.

So, if the highest life total among all players is 40, then the Scourge's power/toughness in the graveyard is -20. This means that for the purposes of Nethroi, Apex of Death, including it as one of the creatures you're returning effectively subtracts 20 from the total power of creatures that you're returning. For example, if your Scourge of the Skyclave is a -20/-20 in the graveyard, you can target it and an Apex Altisaur, Apex Devastator, and Breaker of Armies with Nethroi's ability (since 10 + 10 + 10 - 20 = 10 power between all the creatures you're targeting). The Scourge will of course go back to the graveyard right after it returns, but it's a small price to pay to get effectively 30 power on the battlefield in one fell swoop.

[Argus]

In Commander multiplayer game Scourge of the Skyclaves will have negative values of P/T when it enters the battlefield usually (unless kicked). Am I right these values are the same when Scourge "rots" in graveyard and can account as discount for cards like Nethroi, Apex of Death?

Yes. That's a characteristic-defining ability, so it works in the graveyard.

604.3. Some static abilities are characteristic-defining abilities. A characteristic-defining ability conveys information about an object's characteristics that would normally be found elsewhere on that object (such as in its mana cost, type line, or power/toughness box). Characteristic-defining abilities can add to or override information found elsewhere on that object. Characteristic-defining abilities function in all zones. They also function outside the game.
604.3a A static ability is a characteristic-defining ability if it meets the following criteria: (1) It defines an object's colors, subtypes, power, or toughness; (2) it is printed on the card it affects, it was granted to the token it affects by the effect that created the token, or it was acquired by the object it affects as the result of a copy effect or text-changing effect; (3) it does not directly affect the characteristics of any other objects; (4) it is not an ability that an object grants to itself; and (5) it does not set the values of such characteristics only if certain conditions are met.

And negative values count properly when used in a total.

107.1b Most of the time, the Magic game uses only positive numbers and zero. You can't choose a negative number, deal negative damage, gain negative life, and so on. However, it's possible for a game value, such as a creature's power, to be less than zero. If a calculation or comparison needs to use a negative value, it does so. If a calculation that would determine the result of an effect yields a negative number, zero is used instead, unless that effect doubles or sets to a specific value a player's life total or the power and/or toughness of a creature or creature card.
Example: If a 3/4 creature gets -5/-0, it's a -2/4 creature. It doesn't assign damage in combat. Its total power and toughness is 2. Giving it +3/+0 would raise its power to 1.

Commander Legends® Release Notes

Compiled by Eli Shiffrin and Matt Tabak, with contributions from Laurie Cheers, Tom Fowler, Carsten Haese, Nathan Long, and Thijs van Ommen
Document last modified October 22, 2020

Slaughter the Strong
1WW
Sorcery

Each player chooses any number of creatures they control with total power 4 or less, then sacrifices all other creatures they control.

If a creature's power is somehow less than 0, it subtracts from the total power of the other creatures its controller chooses. This can cause creatures with power 5 or greater to survive.