Immortals Fenyx Rising

This is one that can be unlocked relatively early on with natural progression. You can find gear in Epic Chests in the overworld as well as in the Vaults of Tartaros in which the symbol is a chest with a large suit of armor and helmet behind it (you'll know it when you see it). To identify where these are, you'll want to use a map (such as the excellent interactive one with IGN) or your Far Sight by pressing . Once you have identified them, you will have to battle or solve a puzzle in order to open them.

The first area of the game, Clashing Rocks, has 13 Epic Chests to crack open. The gear you can find here is:
Lion Armor (x2)
Lion Helmet (x2)
Cyclops Armor
Cyclops Helmet
Gorgon Armor
Gorgon Helmet
Satyr Armor
Soldier Armor
Solider Helmet
Boar Armor
Boar Helmet

For the sake of the achievement, you need to focus on any but the Satyr set in order to unlock it. Personally, I found the Lion set easiest to get and will list how to get them below.

Lion Armor
There is a group of small islands to the west of the main area forming a cross and the eastern island is the target with a cave on the west side at sea level. You need to activate the pressure pad with the two metal blocks nearby. One is in the nearby pool which should be brought to the pad. For the second, you must go through an underwater cave by diving down where the bubbles are. At the top of the cave is the block which should be dropped through the nearby hole into the water. Drag this one on the pad and the chest is yours.

Lion Helmet
The helmet is very nearby on the same "cross" islands but now on the southern one; partway up the tall island on the west side in a cave. Again, we need two metal blocks for the pressure pad. One is on the left near a hole in the ceiling over the torch so just grab it down. The second is on the right behind the cracked wall near the ceiling. Climb up and jump then use for a heavy attack to break the wall. Drag this one as well onto the pad and you have the chest.

Lastly, you just need to equip both the Lion Armor and Lion Helmet at the same time through the character screen by pressing and pop goes the cheevo!