Not all that rises is a spirit. The revenant is the body itself, up and walking in its grave-shroud. It is slow - you will see it coming - but it shrugs off what would turn a lesser ghost, and it takes real warding to put back down.
TIP Trade speed for strength: a revenant gives you time to react, so spend it. Ring the bell, get your people inside, and let your wards do the work.