Karn's Sylex
Legendary Artifact
Karn's Sylex enters tapped.
Players can't pay life to cast spells or to activate abilities that aren't mana abilities.
, 
, Exile Karn's Sylex: Destroy each nonland permanent with mana value X or less. Activate only as a sorcery.
Adam Paquette
Dominaria United Promos (PDMU)
• #234sRulings
If a spell or an activated ability that isn’t a mana ability has a cost that requires a player to pay life, that spell or ability can’t be cast or activated.
(wotc • 2022-09-09)
Other things may still cause players to pay life, such as a resolving spell or ability.
(wotc • 2022-09-09)
Players may always pay 0 life, even if an effect says they can’t pay life.
(wotc • 2022-09-09)
Activated abilities contain a colon. They’re generally written “[Cost]: [Effect].” Some keyword abilities are activated abilities (such as cycling) and will have colons in their reminder text.
(wotc • 2022-09-09)
An activated mana ability is one that produces mana as it resolves, not one that costs mana to activate.
(wotc • 2022-09-09)
Rulings
If a spell or an activated ability that isn’t a mana ability has a cost that requires a player to pay life, that spell or ability can’t be cast or activated.
(wotc • 2022-09-09)
Other things may still cause players to pay life, such as a resolving spell or ability.
(wotc • 2022-09-09)
Players may always pay 0 life, even if an effect says they can’t pay life.
(wotc • 2022-09-09)
Activated abilities contain a colon. They’re generally written “[Cost]: [Effect].” Some keyword abilities are activated abilities (such as cycling) and will have colons in their reminder text.
(wotc • 2022-09-09)
An activated mana ability is one that produces mana as it resolves, not one that costs mana to activate.
(wotc • 2022-09-09)