Watcher Sliver

Flying R: This creature gets +1/+0 until end of turn. Suspend 2—RR Whenever an opponent casts a spell, if this card is suspended, that player may put a time counter on this card.

(T: Add U.)

All Sliver creatures have double strike.

Each player loses 1 life, discards a card, sacrifices a creature of their choice, then sacrifices a land of their choice.

All Slivers have "T: Tap target permanent."

Flying Sacrifice this creature: Counter target spell unless its controller pays 2.

All Sliver creatures have "Whenever this creature is dealt damage, put a +1/+1 counter on it." (It must survive the damage to get the counter.)

Flash (You may cast this spell any time you could cast an instant.) When this creature enters, target creature gains first strike until end of turn.