Spells and Spell Creation

[davidseppi]

No: HPFGUIDX 83419

Where do spells originate in the Potterverse?  At the end of GOF, at 
LV's "rebirthing" party, he refers to ancient magic of his own 
creation.  Again, at St. Mungos in OOTP, Harry sees a picture on the 
wall of Someone "can't remember the name," Creator of the Bowel 
Reversal spell.  Is it safe to assume that *all* spells were 
invented?  Harry refers to LV as having the Avada Cadavra curse.  
Does this mean LV invented the curse?

Also, is it safe to assume that really powerful wizards do not need 
to use incantations, are incantations like training wheels?  During 
duel between LV and Dumbledore at the end of OOTP, nary an 
incantation was spoken, yet the power of the spells caused Harry's 
hair to stand on end.  Also, a death eater produces a spell at 
Hermione by simply slashing in the air producing a purplish fire.  We 
later hear that the spell would have been much more powerful if the 
incantation had been spoken.  Perhaps the wizard was not powerful 
enough to properly use an incantationless spell.