Instrumental case (abbreviated as INS) is the grammatical case that marks tools and means of an action. In Nûrlâm it is marked with postposition “-irzi” for declension class I and “-rzi” for declension class II, which can be translated into English as “by”, “by means of”, “with use of”, “using”, “through (use of)”, “via”, etc. Instrumental case changes the role of nouns and pronouns into adverbial. Typical applications of instrumental case in Nûrlâm include:

• to indicate instrument of an action (“I cut the tree with an axe”, “send by (messenger) raven”));
• to indicate the agent of passive action expressed by passive participle (“The tree was cut by me”). This function was borrowed from archaic Ergative case with similar ending “-irz”.
• locative function denoting motion through the object or some media (“they came by the sea”), may be further clarified by adding postposition “tuk” (through);
• make distributive numerals (“one by one”, “stand by fours”);
• used together with prepositions “ik” or “zi” to denote ending of an action before/by some time, (“They all will be killed by the dawn”). Please note, that preposition “ugil” with similar meaning requires noun in accusative case

Instrumental case is not used when translating preposition “by” from English in following cases:

• locative function with stationary meaning “near(by)” (“house by the sea”) - replace with noun in Allative case together with postposition “mush”;

Instrumental case should not be mixed with comitative case. While both may be translated into English with preposition “with”, comitative case is used when word “together” may be added before it without affecting the sense. “Sauron conquered Gondor (together) with Saruman” vs. “Sauron conquered Gondor with aid of Saruman”.