As far as we know, there are only three HUD systems.

One for the dungeon cores, one for the sentient races, and one for contracted creatures.

Dungeon core HUD.

Not much is known about them. We do know that they have no level limit like the rest. Every 100 levels they can make a new dungeon core. Besides that, everything else is a complete mystery.

Sentient race HUD.

We know much more about the sentient HUD since every elf has it. The level cap is 20 and is more along the lines of caring around the grimoire. What I mean by grimoire is that it carries the information on how to cast spells.

Almost all spells can be taught. There are a few exceptions, like the Ranger ability radar, It can be used to track down enemies, but no other class can learn this ability. However, empowered arrows can be acquired by everyone. One of the greatest alchemists of our generation wasn't even an alchemist class. He had the crafter class. Through training and hard work, he learned most of the skills needed for alchemy.

There are dozens of different classes, and each class has its own class-specific abilities that cannot be taught. Each class may only have one or two class-specific skills.

Most people get their class at the age of six. The class Is determined by the activities they enjoy doing the most or is determined by bloodline. Classes that only come from a bloodline can be overwritten if the child works hard enough before the age of six.

Contracted creatures HUD.

Instead of this HUD focusing on knowledge like the sentient race HUD. This one focuses on upgrading the physical abilities of the creature or monster. All monsters have this HUD in this HUD gives them their unique skills. For instance, bears usually are harmless until they reach the age of 10. Then they get access to the HUD and will turn into a specialized monster like an armored bear or an elemental bear.

If you do manage to make a contract with a monster or creature you'll be able to access their HUD and choose what upgrades they get in the future. This is an excellent asset for beast tamers because it means will never have to worry about our family pets or regular riding mounts turning into horrifying monsters in the middle of the night.

Creatures and monsters level caps are determined by their overall potential, and This means a squirrel can have a maximum level of two, whereas a dragon can have a Max level of 500. Most of their levels are earned either through fighting or merely going about their daily lives, such as running away from a predator or eating grass out in the field.