2018-07-13 : Players can respond only once Thud has been cast and all its costs have been paid. No one can try to destroy the creature you sacrificed to prevent you from casting this spell.

2018-07-13 : The sacrificed creature’s last known existence on the battlefield is checked to determine its power.

2018-07-13 : You must sacrifice exactly one creature to cast Thud; you can’t cast it without sacrificing a creature, and you can’t sacrifice additional creatures.