When a creature tries to Move through a hostile target's space, the mover can try to push or tumble its way through the hostile target's space.
This only needs to be done typically in combat. However, if you try to push past a creature that is potentially hostile, this could trigger initiative determined by GMD.
A caster can only do this once per turn, and is stopped at the first failure of trying to traverse through a hostile space at -1 or +1 x-position (which ever is shorter), this also has to be an open space in the XZ System.
The clash of bodies surges like a breaking tide—limbs press, torsos jostle, and space narrows. Each step forward grinds against resistance, forcing momentum through the shifting gaps of unyielding forms, every movement a battle for inches.