Static abilities that prevent damage (including protection abilities) don't do so. If they have additional effects that don't depend on the amount of damage prevented, those additional effects will still work. Such effects are applied only once per source of damage.

If an effect says to set a player's life total to a certain number, and that number is higher than the player's current life total, that part of the effect won't do anything. (If the number is lower than the player's current life total, the effect will work as normal.)

Damage prevention shields don't have any effect. If a prevention effect has an additional effect, the additional effect will still work (if possible). Spells that create prevention effects can still be cast, and abilities that create prevention effects can still be activated.

Effects that would replace gaining life with some other effect won't be able to do anything because it's impossible for players to gain life.

Spells and abilities that would normally cause a player to gain life still resolve, but the life-gain part simply has no effect.

Effects that replace an event with gaining life (like Words of Worship's effect does) will end up replacing the event with nothing.

Effects that replace or redirect damage without using the word "prevent" are not affected by Leyline of Punishment.

If a creature is dealt lethal damage, it can still regenerate. If it does, the damage marked on it will be removed from it.

If a cost includes life gain (like Invigorate's alternative cost does), that cost can't be paid.

A player's "opening hand" is the hand of cards the player has after all players have taken mulligans. If players have any cards in hand that allow actions to be taken with them from a player's opening hand, the starting player takes all such actions first in any order, followed by each other player in turn order. Then the first turn begins.