HasteHaste is a static ability.
If a creature has haste, it can attack even if it hasn’t been controlled by its controller continuously since their most recent turn began. (See rule 302.6.)
If a creature has haste, its controller can activate its activated abilities whose cost includes the tap symbol or the untap symbol even if that creature hasn’t been controlled by that player continuously since their most recent turn began. (See rule 302.6.)
Multiple instances of haste on the same creature are redundant. (CR 702.10)
ProwessProwess is a triggered ability. “Prowess” means “Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.”
If a creature has multiple instances of prowess, each triggers separately. (CR 702.108) (Whenever you
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) a noncreature spell, this creature gets +1/+1 until end of turn.)
ValiantAn ability word has no rules meaning of its own. It groups abilities with similar themes; the text following it explains this card’s effect. (CR 207.2c) — Whenever this creature becomes the target of a spell or ability you control for the first time each turn,
exileTo exile an object, move it to the exile zone from wherever it is. See rule 406, “Exile.” (CR 701.13) the top card of your library. Until end of turn, you may
playTo play a land means to put it onto the battlefield from the zone it’s in (usually the hand). A player may play a land if they have priority, it’s the main phase of their turn, the stack is empty, and they haven’t played a land this turn. Playing a land is a special action (see rule 116), so it doesn’t use the stack; it simply happens. Putting a land onto the battlefield as the result of a spell or ability isn’t the same as playing a land. See rule 305, “Lands.”
To play a card means to play that card as a land or to cast that card as a spell, whichever is appropriate.
Some effects instruct a player to “play” with a certain aspect of the game changed, such as “Play with the top card of your library revealed.” “Play” in this sense means to play the Magic game.
Previously, the action of casting a spell, or casting a card as a spell, was referred to on cards as “playing” that spell or that card. Cards that were printed with that text have received errata in the Oracle card reference so they now refer to “casting” that spell or that card.
Previously, the action of using an activated ability was referred to on cards as “playing” that ability. Cards that were printed with that text have received errata in the Oracle card reference so they now refer to “activating” that ability. (CR 701.18) that card.