I know many secrets...
Henzell says...
  1. Enhancers improve spell power. They are items such as rings of fire or ice; staves of conjuration, fire, etc; or robes of the archmagi. x1.5 spell power per item, stacked multiplicatively up to a maximum of 3 items. However, there is a diminishing returns effect at high spellpower.
  2. Normal enhancers are capped at 3 (getting 4 is hard anyway). Other effects such as wild magic or augmentation aren't counted for purposes of this cap.

Information based on master branch and the great LearnDB.
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