Ride Down

Instant

Destroy target blocking creature. Creatures that were blocked by that creature this combat gain trample until end of turn.

2014-09-20:
The attacking creatures that the destroyed creature was blocking remain blocked (even if no other creatures were blocking them). An attacking creature with trample that has no creature blocking it can deal its combat damage to the defending player or planeswalker.
2014-09-20:
In some rare cases, the blocking creature wasn’t declared as a blocking creature that combat (for example, if it entered the battlefield blocking). In that case, the attacking creatures it was blocking won’t gain trample even though the blocking creature is destroyed.
2016-07-13:
The attacking creatures that the destroyed creature was blocking remain blocked (even if no other creatures were blocking them). An attacking creature with trample that has no creature blocking it will deal its combat damage to the defending player or planeswalker.