First strikeFirst strike is a static ability that modifies the rules for the combat damage step. (See rule 510, “Combat Damage Step.”)
If at least one attacking or blocking creature has first strike or double strike (see rule 702.4) as the combat damage step begins, the only creatures that assign combat damage in that step are those with first strike or double strike. After that step, instead of proceeding to the end of combat step, the phase gets a second combat damage step. The only creatures that assign combat damage in that step are the remaining attackers and blockers that had neither first strike nor double strike as the first combat damage step began, as well as the remaining attackers and blockers that currently have double strike. After that step, the phase proceeds to the end of combat step.
Giving first strike to a creature without it after combat damage has already been dealt in the first combat damage step won’t preclude that creature from assigning combat damage in the second combat damage step. Removing first strike from a creature after it has already dealt combat damage in the first combat damage step won’t allow it to also assign combat damage in the second combat damage step (unless the creature has double strike).
Multiple instances of first strike on the same creature are redundant. (CR 702.7),
hexproofHexproof is a static ability.
“Hexproof” on a permanent means “This permanent can’t be the target of spells or abilities your opponents control.”
“Hexproof” on a player means “You can’t be the target of spells or abilities your opponents control.”
“Hexproof from [quality]” is a variant of the hexproof ability. “Hexproof from [quality]” on a permanent means “This permanent can’t be the target of [quality] spells your opponents control or abilities your opponents control from [quality] sources.” A “hexproof from [quality]” ability is a hexproof ability.
Any effect that causes an object to lose hexproof will cause an object to lose all “hexproof from [quality]” abilities. Any effect that allows a player to choose a creature with hexproof as a target as though it didn’t have hexproof will allow a player to choose a creature with a “hexproof from [quality]” ability. Any effect that looks for a card with hexproof will find a card with a “hexproof from [quality]” ability.
“Hexproof from [quality A] and from [quality B]” is shorthand for “hexproof from [quality A]” and “hexproof from [quality B]”; it behaves as two separate hexproof abilities.
“Hexproof from each [characteristic]” is shorthand for “hexproof from [quality A],” “hexproof from [quality B],” and so on for each possible quality the listed characteristic could have; it behaves as multiple separate hexproof abilities.
Multiple instances of the same hexproof ability on the same permanent or player are redundant. (CR 702.11)
Whenever Narset attacks,
exileTo exile an object, move it to the exile zone from wherever it is. See rule 406, “Exile.” (CR 701.13) the top four cards of your library. Until end of turn, you may
castTo cast a spell is to take it from the zone it’s in (usually the hand), put it on the stack, and pay its costs, so that it will eventually resolve and have its effect. A player may cast a spell if they have priority. See rule 601, “Casting Spells.”
To cast a card is to cast it as a spell. (CR 701.5) noncreature spells from among those cards without paying their mana costs.