Nadir is a Runeword "NefTir" in Diablo 2 Resurrected (D2R). It requires these 2 runes to be inserted into a socketed item in the exact order: Nef + Tir . The eligible bases for Nadir are the following: Helms, Barbarian Helms, Circlets, Druid Pelts . This is the only Runeword in the game that has -X% Extra Gold from Monsters attribute.
NadirNadirBone Helm
Nef · Tir
Defense: 65
Durability: 40 of 40
Required Strength: 25
Required Level: 13
+50% Enhanced Defense
+10 Defense
+30 Defense Vs. Missile
Level 13 Cloak of Shadows (9/9 Charges)
+2 to Mana after each Kill
+5 to Strength
-33% Extra Gold from Monsters
-3 to Light Radius
Socketed (2)
Trade items on d2trader.net

How to obtain Nadir

The fastest way to get this item on Battle.net is via trading, you can use the Item Price Checker to see how much Nadir is worth.
Another way of getting this Runeword is by farming the runes and the base. Find the drop rates of these items in the Item Database.

Nadir bases

The best base for Nadir is Bone Helm. Below is a list of all eligible 2 socket bases for Nadir.