Kalar 💚

A black, open balaclava. It covers most of the head, but leaves the face partially exposed—one of the most noticeable features.
Sunglasses. They add a cool, aloof look to the character.
Transparent protective goggles on his helmet. This detail suggests he's prepared for various mission hazards.
A bright yellow bandage on his arm. This is an important marker: it immediately identifies his group (Fireteam 6) or rank. Incidentally, in the game, he also has a yellow health bar—this is also part of his visual identity.
Light stubble. It gives him a more experienced, "worn-out" look.
A barely noticeable smile or grin. It's not just a smirk: the developers visually emphasize his optimistic nature—even in tense situations, he tries to see the bright side.
A triangular haircut. Another small but noticeable detail of his appearance. He has yellow skin, a yellow headband, and a helmet with yellow life stripes on the sides. He's 25.

Hellmet is the name of a Roblox game. Kaska, however, is one of the characters within it. So, "kaska" in this case isn't a type of protective headgear in the real world, but the name of the character. The name itself is no coincidence: the word "kaska" actually translates as "helmet" (in Russian, Polish, Bulgarian, and Albanian).

What is he like, Casca?
I have selected the main features of this character:

Role in the game: He is a member of Fireteam 6 and is often considered the second most important member of the squad.
Appearance: He wears a black, open balaclava (it covers most of his head, but leaves his face partially exposed), sunglasses, and clear goggles on his helmet. He also has a bright yellow armband, which makes him instantly recognizable. Casca also has a light stubble and a subtle smirk, which underscores his confidence.
Personality: He's a hybrid of both. He's sarcastic and occasionally blunt (especially when confronted with incompetence), yet relaxed and optimistic—in tense situations, he tries to see the bright side and encourages his comrades. He can be a bit mischievous in conversation: for example, during missions, he addresses the squad leader, Aradus, as "Boss," and Kalar as "Kid."
Background: His real name is Kaden Jedaman, and he was born on October 8, 1999. As a child, he grew up on his father's ranch and even then showed a talent for marksmanship (even winning local stone-throwing competitions). Later, during the Gesan civil wars, he signed on with the Nusian military, served in an assault team, and then joined Fireteam 6.
Funny details: There's a joke in the game: Casca is supposedly addicted to "healthpens" (in-game items used to restore health). He constantly asks his comrades if they have any.

Clothing and equipment. He wears an open black balaclava, leaving his face partially exposed. He wears clear goggles pushed up onto his helmet. He wears a green armband on his left arm. His attire is tactical: a green checkered shirt under a voluminous vest with pouches, green pants, and boots. He wears a dark tactical helmet with green illuminated night vision attachments and a headset with a microphone.
Game detail: A green health bar hovers above the character—this is a feature of the HELLMET interface.

Aradus is the leader of Fireteam 6, which the user plays as. Incidentally, when a player creates a lobby, they automatically assume the role of Aradus.
Appearance. The character's face is hidden (only his eyes are visible), he wears a balaclava, a blue headband, and night vision goggles (Chimera NVGs—in Roblox, these are more for show than for in-game bonuses). He has a blue health bar on his helmet.
Personality. Stern and hot-tempered, with a combat background. He's not afraid to pressure his superiors to extract the information he needs, but deep down, he cares about his subordinates. Different missions reveal different sides of him: in some, he's focused on the mission, while in others, he can lose his temper—and then his comrades (like Pronto or Kalar) stop him. He sometimes allows himself to joke (in the mission "Decovenant," he called Casca a "homeless person").
Past. He was likely conscripted into the Nusian army at a young age; he's a war veteran and possibly suffered an injury—this is reflected in his manner of speech. At some point, he befriended Pronto. During the events of Decovenant, Aradus, along with Kalar, found Kask, and his comrades elected him leader of Fireteam 6.

His real name is Arden Salamasi. He is a new recruit in the Nusian Army and a member of Fireteam 6. Kalar is naive, young, and inexperienced, yet selfless and capable. One of his most striking traits is that if someone on the team (or he himself) kills a non-hostile character, he exclaims, "NO!" In one mission, he even tries to teach Casca a phrase in the Gesan language. Among his phrases is, "If I fail, please find my parents."

About the helmet
In the game, characters actually have different tactical helmets. Originally, Kalar (then called Spick) wore an ACH (Advanced Combat Helmet). The character's name was later changed, likely because "Spick" sounds similar to a racial slur in the Clothing and Equipment section. He wears an open black balaclava, leaving his face partially exposed. He wears transparent goggles pushed up onto his helmet. He wears a green armband on his left arm. His attire is tactical: a green checkered shirt under a bulky vest with pouches, green pants, and boots. He wears a dark tactical helmet with green glowing night vision attachments and a headset with a microphone.
Game detail: A green health bar hovers above the character—a feature of the HELLMET interface. He has a green headband on his military uniform, yellow hair, yellow skin, and is 19 years old.