Bearer of Silence
Creature — Eldrazi
Devoid (This card has no color.)
When you cast this spell, you may pay 
. If you do, target opponent sacrifices a creature. ( represents colorless mana.)
Flying
This creature can't block.
Tyler Jacobson
Rulings
Players can respond to the triggered ability, but once it starts resolving and you decide whether to pay {1}{C}, it's too late for anyone to respond.
(wotc • 2016-01-22)
Bearer of Silence's triggered ability targets only the player, not any creature. For example, the player may sacrifice a creature with hexproof.
(wotc • 2016-01-22)
Rulings
Players can respond to the triggered ability, but once it starts resolving and you decide whether to pay {1}{C}, it's too late for anyone to respond.
(wotc • 2016-01-22)
Bearer of Silence's triggered ability targets only the player, not any creature. For example, the player may sacrifice a creature with hexproof.
(wotc • 2016-01-22)