-r nominative plural ending regularly used on nouns ending in -a, -i, -ië, -o, -u, e.g. Ainur, Valar, tier. Occasionally it is added also to nouns ending in -ë (that normally take the ending -I in the pl.). This seems to regularly happen in the case of nouns in -lë (see #fintalë, mallë, tyellë), sometimes also otherwise (see Ingwë, wendë, essë #1). This plural ending was ("it is said") first used by the Noldor (PM:402).
Quenya
fintalë
trick
fintalë
noun. trick
-a
it is said
#fintalë noun "trick", given as pl. fintaler (PE17:119)