The Frolum's Ring artifact can be found at Harad Basin, in the south-eastern part of Sea of Núrnen.
Frolum's Ring, First Age.
This ring was given to the unhappy bandit Frolum by his beloved wife as a symbol of their undying love. It was violently pulled from Frolum's hand, along with his index finger after his capture by the Dark Lord Sauron's minions. Sauron would use this ring to torment Frolum into betraying his comrades.
"Who's this now?
Some unhappy bandit. Name's Frolum or Gorfab or something. He was screaming for his wife. The boys laid into 'im a bit.
More'n a bit. He dead?
Naw. The boys know the big man's powerful livid and wants a word. This sack of dung might know where his thief pals are hiding.
Strip him down. Take the ring, too, and give it to the boss; he likes that stuff. And when he wakes up…"