Marang River Prowler can't block and can't be blocked. You may cast Marang River Prowler from your graveyard as long as you control a black or green permanent.
The currents of the Marang wash away both tracks and blood.
2018-12-07
Marang River Prowler checks if you control a black or green permanent only as you begin to cast it. Once you begin to cast Marang River Prowler from your graveyard, it doesn't matter what happens to the black or green permanents you control.
2018-12-07
You must follow the normal timing permissions and restrictions and pay its cost to cast Marang River Prowler from your graveyard.