Some spells and abilities have additional costs. An additional cost is a cost listed in a spell’s rules text, or applied to a spell or ability from another effect, that its controller must pay at the same time they pay the spell’s mana cost or the ability’s activation cost. Note that some additional costs are listed in keywords; see rule 702.
May 3, 2019 · War of the Spark
If an effect says that a player can’t lose life, that player can’t make an exchange such that the player’s life total would become lower; in that case, the exchange won’t happen. Similarly, if an effect redistributes life totals, a player can’t receive a new life total such that the player’s life total would become lower. In addition, a cost that involves having that player pay life can’t be paid.
January 25, 2019 · Ravnica Allegiance
If an effect says that a player can't lose life, that player can't make an exchange such that the player's life total would become lower; in that case, the exchange won't happen. Similarly, if an effect redistributes life totals, a player can't receive a new life total such that the player's life total would become lower. In addition, a cost that involves having that player pay life can't be paid.
January 20, 2017 · Aether Revolt
If an effect says that a player can’t lose life, that player can’t make an exchange such that the player’s life total would become lower; in that case, the exchange won’t happen. Similarly, if an effect redistributes life totals, a player can’t receive a new life total such that the player’s life total would become lower. In addition, a cost that involves having that player pay life can’t be paid.
February 1, 2014 · Born of the Gods
If an effect says that a player can’t lose life, that player can’t make an exchange such that the player’s life total would become lower; in that case, the exchange won’t happen. In addition, a cost that involves having that player pay life can’t be paid.
May 1, 2012 · Avacyn Restored
If an effect says that a player can't lose life, that player can't make an exchange such that the player's life total would become lower; in that case, the exchange won't happen. In addition, a cost that involves having that player pay life can't be paid.
September 30, 2011 · Innistrad
If an effect says that a player can't lose life, that player can't exchange life totals with a player who has a lower life total; in that case, the exchange won't happen. In addition, a cost that involves having that player pay life can't be paid.
June 17, 2011 · Commander 2011
If an effect says that a player can’t lose life, that player can’t exchange life totals with a player
April 1, 2011 · Duel Decks: Knights vs. Dragons
If an effect says that a player can't lose life, that player can't exchange life totals with a player who has a lower life total; in that case, the exchange won't happen. In addition, a cost that involves having that player pay life can't be paid.
February 4, 2011 · Mirrodin Besieged
If an effect says that a player can’t lose life, that player can’t exchange life totals with a player who has a lower life total; in that case, the exchange won’t happen. In addition, a cost that involves having that player pay life can’t be paid.
October 1, 2010 · Scars of Mirrodin
If an effect says that a player can’t lose life, that player can’t exchange life totals with a player
July 16, 2010 · Magic 2011
Some triggered abilities are written, "Whenever [a player] gains life, . . . ." Such abilities are treated as though they are written, "Whenever a source causes [a player] to gain life, . . . ."
February 1, 2010 · Worldwake
If a source would deal 0 damage, it does not deal damage at all. That means abilities that trigger on damage being dealt won't trigger. It also means that replacement effects that would increase the damage dealt by that source, or would have that source deal that damage to a different object or player, have no event to replace, so they have no effect.