Longinus' Hand has the appearance of a giant hand that can be used to flatten massive amounts of land. On Mu-Bong, it has the appearance of a cross on each of his hands.
Longinus' Hand can be used to flatten large areas by summoning the hand and smashing the landscape with it. It is essentially like having the hand of a giant.
Gravity: Longinus' Hand can be used to bring down buildings among other things with an increased gravitational pull at those points. It can also reverse the gravity around some area, levitating objects. Mu-Bong's skill in this ability is such he can change the topography in a tunnel without it collapsing.
Shield: Longinus' Hand can be used as a shield. Mu-Bong puts his hand out and a large cross gets emitted that blocks most attacks. It is unclear how this power works.