As an additional cost to
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) this spell,
sacrificeTo sacrifice a permanent, its controller moves it from the battlefield directly to its owner’s graveyard. A player can’t sacrifice something that isn’t a permanent, or something that’s a permanent they don’t control. Sacrificing a permanent doesn’t destroy it, so regeneration or other effects that replace destruction can’t affect this action. (CR 701.21) an artifact or creature.
Ward Ward is a triggered ability. Ward [cost] means “Whenever this permanent becomes the target of a spell or ability an opponent controls, counter that spell or ability unless that player pays [cost].”
Some ward abilities include an X in their cost and state what X is equal to. This value is determined at the time the ability resolves, not locked in as the ability triggers. (CR 702.21)
When this artifact enters,
exileTo exile an object, move it to the exile zone from wherever it is. See rule 406, “Exile.” (CR 701.13) target artifact or creature an opponent controls until this artifact leaves the battlefield.