Altar of Intercession

Whenever a creature an opponent controls attacks you or
a planeswalker you control, you may pay {2}. If you do,
exile that creature until Altar of Intercession leaves the
battlefield.
When Altar of Intercession leaves the battlefield, return all
cards exiled with it to the battlefield under their owners'
control.
If no cards are exiled with Altar of Intercession, sacrifice it.

Its sanctuary stands not only for prayer, but as a warning to
those who would profane sacred ground.