Special modifiers are bonuses found on such items as [[uniques]], [[runewords]], and [[Item SetsSet Items]], but not on [[magical]] or [[rare]] items. They are not like other [[prefixes]] or [[suffixes]]. These bonuses are picked from a pre-set list, not randomly-generated, and not randomly valued either. There aren't multiple types or levels of Crushing Blow, or ITD; it's there or it's not, to whatever value is preset.
These modifiers do not have Clvl requirements or Ilvls, like prefixes and suffixes do, and the character level required to use these items will always be pre-determined on Uniques and Set Items. On Crafted Items the Clvl can be pre-set, but is usually determined by the random mods (since they're usually higher than the minimum preset value).