Toadskin Leg Guards

Feet, item level 30. Equip level 30, Disciple of War.

From 177 Proof of Might and 3 more quests.

From quests

177 Proof of MightChoose one of 5
177 The One That Got AwayChoose one of 5
171 Return of the HolyfistChoose one of 5
165 Cloying VictoryChoose one of 5

Other databases

Eorzea Database (the official one, on The Lodestone)
Console Games Wiki
Garland Tools (vendors, crafting, drops)