The fact that its strictly worse than Midnight Haunting unless we can generate black mana means that its a very archetype specific card, though it will almost certainly see play in Standard
Because shock lands have land types (Plains, Island, Swamp, Mountain, Forest), they are searchable with fetch lands, forming a powerful mana-fixing duo
Even if you do, -15 probably leaves Gideon with such low loyalty that you can't close out the game before everyone rebuilds
Fetch lands (this is one of my only decks that uses them
Furthermore, it costs three mana and a creature just to get a 3/3 out of it
Bloomburrow'sYgra, Eater of Allturns every other creature into Food, and leads this deck filled with sacrifice synergies that converts them into all sorts of extra value