Her -2 ability reads Target player sacrifices a creature. If your opponent used this ability when you have hexproof, theyd be forced to target themselves by default since you couldnt be targeted
In fact, many planeswalkers give you game against burn, whether by gaining life, by removing their threats, or just by preserving your life total by being attacked instead
Value-wise it's also the biggest card there
Ground types resist 2 types, which they receive half damage from: Poison - Cant harm inorganic materials, like dirt and sand
Eventually madness cards enter the graveyard
Shadowspear helps ensure you have consistent access to lifegain and trample for your ring bearer, with the side benefit of letting you remove hexproof and indestructible from opposing threats, and can be searched up with Urzas Saga