this is gus also known as the black swordsman

After receiving the Berserker Armor, Guts receives a small fringe of white on his hair, presumably due to the stress brought on from wielding the armor. Guts tendency to wear black clothing while hunting the apostles gained him the nickname "The Black Swordsman".

this is the berserk armor owned by gus

The Berserker Armor is a cursed suit of Armor which gives the wearer incredible strength, endurance and the ability not to feel pain. It does this by allowing its users to bypass the natural subconscious limits that prevent them from injuring themselves when using their full strength

what is a apostle?

Apostles are inhumans who, typically having acquired and activated a behelit in a moment of anguish, summoned the God Hand and joined the ranks of demonkind in exchange for a precious sacrifice.

what is a behelit?

Purpose The Behelit is actually a key used by mankind to summon the God Hand, a group of immensely powerful angels (or demons), themselves the servants of a dark God that governs the Berserk universe.