WardWard 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)—You get two
poison countersA player with ten or more poison counters loses the game. (CR 704.5c).
AnnihilatorAnnihilator is a triggered ability. “Annihilator N” means “Whenever this creature attacks, defending player sacrifices N permanents.”
If a creature has multiple instances of annihilator, each triggers separately. (CR 702.86) X, where X is the total number of
poison countersA player with ten or more poison counters loses the game. (CR 704.5c) your opponents have.
When 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) That Which Was Compleated, you may put a card an opponent owns in
exileTo exile an object, move it to the exile zone from wherever it is. See rule 406, “Exile.” (CR 701.13) into their graveyard. If you do, they get two
poison countersA player with ten or more poison counters loses the game. (CR 704.5c).