Quenya 

-nen

most nouns have an instrumental in -nen

-nen instrumental ending (pl. -inen, dual -nten, partitive pl. -línen). Attested in ambartanen, lírinen, lintieryanen, súrinen, parmanen; see ambar (#2), lírë, lintië, súrë, parma. Tolkien noted that "most nouns have an instrumental in -nen" (PE17:62), a wording suggesting that the form of the ending may vary; given the normal development ln > ld, it is possible that it would appear as *-den when added to a noun in -l (*macilden "with a sword").