Dreadful Gladiator's Investiture is the Season 12 Death Knight arena set. This set is sold by the following vendors for 10,250 Honor Points:
Horde: Lok'nor Bloodfist in Kun-Lai Summit
Alliance: Hayden Christophen in Valley of the Four Winds. It contains 5 pieces. Has set bonuses at 2 and 4 pieces.
Dreadful Gladiator's Dreadplate Chestpiece
Dreadful Gladiator's Dreadplate Gauntlets
Dreadful Gladiator's Dreadplate Helm
Dreadful Gladiator's Dreadplate Legguards
Dreadful Gladiator's Dreadplate Shoulders
Wearing more pieces of this set will convey bonuses to your character:
2 pieces: Whenever you are struck by a movement-impairing effect, you will generate 3 Runic Power every 1 sec for 5 sec.
4 pieces: For 3 sec after casting Death Grip, you may cast the spell a second time without regard for its cooldown.
By obtaining parts of this set you'll increase your stats and be more powerful
Here you can buy Season 12 Death knight Dreadful Gladiator's Desecration for EU or US Servers.
You'll get guide for getting Season 12 Death knight Dreadful Gladiator's Desecration