Tymaret, Chosen from Death — ruling 1

The ability that defines Tymaret's toughness works in all zones, not just the battlefield.

Tymaret, Chosen from Death — ruling 2

Because damage remains marked on a creature until the damage is removed as the turn ends, nonlethal damage dealt to Tymaret may become lethal if your devotion to black decreases during that turn.

Tymaret, Chosen from Death — ruling 3

Colorless and generic mana symbols ({C}, {0}, {1}, {2}, {X}, and so on) in mana costs of permanents you control don't count toward your devotion to any color.

Tymaret, Chosen from Death — ruling 4

Mana symbols in the text boxes of permanents you control don't count toward your devotion to any color.

Tymaret, Chosen from Death — ruling 5

Hybrid mana symbols, monocolored hybrid mana symbols, and Phyrexian mana symbols do count toward your devotion to their color(s).

Tymaret, Chosen from Death — ruling 6

If an activated ability or triggered ability has an effect that depends on your devotion to a color, you count the number of mana symbols of that color among the mana costs of permanents you control as the ability resolves. The permanent with that ability will be counted if it's still on the battlefield at that time.

Tymaret, Chosen from Death — ruling 7

If you put an Aura on an opponent's permanent, you still control the Aura, and mana symbols in its mana cost count towards your devotion.

Tymaret, Chosen from Death : règles, fonctionnement et interactions (MTG)

Tymaret, Chosen from Death 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

Tymaret's toughness is equal to your devotion to black. (Each in the mana costs of permanents you control counts toward your devotion to black.) : Exile up to two target cards from graveyards. You gain 1 life for each creature card exiled this way.

How it works : Tymaret, Chosen from Death

Original English text — Wizards of the Coast / Scryfall

#1January 24, 2020· Wizards of the Coast
The ability that defines Tymaret's toughness works in all zones, not just the battlefield.
No other card is named in this ruling.
#2January 24, 2020· Wizards of the Coast
Because damage remains marked on a creature until the damage is removed as the turn ends, nonlethal damage dealt to Tymaret may become lethal if your devotion to black decreases during that turn.
No other card is named in this ruling.
#3January 24, 2020· Wizards of the Coast
Colorless and generic mana symbols (, , , , , and so on) in mana costs of permanents you control don't count toward your devotion to any color.
No other card is named in this ruling.
#4January 24, 2020· Wizards of the Coast
Mana symbols in the text boxes of permanents you control don't count toward your devotion to any color.
No other card is named in this ruling.
#5January 24, 2020· Wizards of the Coast
Hybrid mana symbols, monocolored hybrid mana symbols, and Phyrexian mana symbols do count toward your devotion to their color(s).
No other card is named in this ruling.
#6January 24, 2020· Wizards of the Coast
If an activated ability or triggered ability has an effect that depends on your devotion to a color, you count the number of mana symbols of that color among the mana costs of permanents you control as the ability resolves. The permanent with that ability will be counted if it's still on the battlefield at that time.
No other card is named in this ruling.
#7January 24, 2020· Wizards of the Coast
If you put an Aura on an opponent's permanent, you still control the Aura, and mana symbols in its mana cost count towards your devotion.
No other card is named in this ruling.