In The Burning Crusade it is item level 115 and requires level 70. In Wrath of the Lich King it is item level 251 and requires level 80. In MoP Classic it is item level 115 and requires level 70.
Read from the World of Warcraft client build files (JournalEncounterItem, JournalEncounterCreature, Achievement) and the Blizzard Game Data quest API.
How Fiend Slayer Boots Compares
Who It Suits
Mail is the armor type Evoker, Hunter and Shaman wear. With Agility or Intellect, Fiend Slayer Boots suits Beast Mastery, Marksmanship and Survival Hunter; Elemental, Enhancement and Restoration Shaman; Devastation, Preservation and Augmentation Evoker.
Transmog Sets
Fiend Slayer Boots is part of the transmog set Demon Stalker Armor (Hunter only). The other 9 pieces:
Blizzard numbers items as they are created, so the named items next to ID 28746 (28741 to 28751) were usually added in the same batch as Fiend Slayer Boots: the same quest line, zone, vendor or reward set.