Erf, possibly derived from the word "Earth", tends to deal with the physical, tangible, and practical. Findamancy locates a unit, object, or location that exists. Turnamancy affects a unit's Loyalty or a city's unit production. Dirtamancy creates and heals golems from available material, and can move and restructure the Erf itself. Lookamancy allows you to see a distant location as it is at that moment. Flower Power and Shockmancy have direct effects on units. Hat Magic creates magic hats and transports physical matter. Least clearly physical is Luckamancy, which seems to directly affect reality.
Speculation on Erf in Magic
Fate controls the paths of units and sides. Numbers deals in likelihoods and abstracts. Erf is the world around you, the terrain, reality itself. Looking at each possibility of Erf + Life + Motion + Matter
Luckamancy - Erf alone. Devoid of the influences of Fate and Numbers (Predictamancy and Mathamancy), untied to Life, Motion, or Matter (which seek to change or control), luckamancy is free to do the impossible. Or not.
Lookamancy - Erf, Life, and Motion (no Matter)- Watching the motion of life on erf. Observing its changes.
Flower Power - Erf, Life, and Matter (no Motion)- Maintaining life, preserving matter... the absence of motion. No change. Flaking. Time standing still.
Shockmancy - Erf, Motion, and Matter (no Life) - Change or movement of matter, absence of Life. Shock and awe.
Hat Magic - Erf, Life, Motion, and Matter - Transmission of matter and knowledge (life) across the erf.
augmented upon the notes on the discussion page by Commander I. Heartly Noah June 3 2009