Eternity is a Rank A Sword made from Diamond.
|Element||- - - - - - -|
|Fused from 3||Bling-bling|
|Attack Points (AP)||42|
|Defense Points (DP)||10|
|Sell Price (Sword Coins)||60,000|
|Sword Contest Points||270|
The person appears to be the Wanderer (who is probably the same person in both Prehistoric Vow, Nieves, And Nameless manga page). He places the sword into a pedestal in the midst of rain. There it will stand...for all eternity.
As you may have guessed, the name 'Eternity' represents the Diamond., which takes forever to create and is probably why the sword in Eternity gets shinier and more clear the longer it is in place.
Of note is the headstone nearby, suggesting that the Wanderer has left the sword as a kind of monument to a fallen warrior or friend.