Warden seem similar to warforged from D&D. What exactly are they?

Gonna send you a few copy pastes from prior lore/world building that may (or may not in the future) be relevant:

Wardens in this setting are a race created by the Earth spirit, Gnome, in the early ages where Orcs, Blanks, and Fawnae were the only other beings on the planet. The Wardens role were to purify the land so that it can be inhabited by the other races. Shell shedding is a method used to purify an area, where the shell is buried in the ground as a short ritualistic type thing.
Thus, the premise of this is to drive out any dangerous forces, and make land inhabitable with fertile soil, plantlife, and whatnot.
In Knight & Rogue, you are told that this is what the Wardens did, and after their work was no longer needed, Gnome allowed them to live as their own race, as this earthbound race was already humanoid enough and overtime gained emotion shared by the other races. So there'd probably be a day dedicated to the Wardens on the day Gnome gave their blessing to them.
You'd also learn that through the combined efforts of all 4 spirits, that's how humans, elves, and dwarves were created.
Warden is to Earth/Gnome
Orc is to Water/Undine
Fawnae is to Fire/Ifrit
Blank is to Wind/Sylph

Warden = land responsibilities, somewhat robotic, blessed by Gnome to become their own race. iow granted the ability to reproduce.

Physically, they sorta have this exoskeleton thing goin' on and they resemble suits of armor, thus how they got their name. Their most distinct features are their helmet-like heads fancied up with some spikes or horns and a plume. The torso is very defined, resembling that of a well-built human. Out-of-shape knights have their exoskeletons stretched (for the fatties) or shrunken (for the scrawnies) but overall still keep that well-built look, and yes, they do molt. Think of them as bugs, without actually being a bug.
Their exoskeletons usually take muted earthy or metallic colors while their plumes are sometimes a bit more vibrant. Their eyes glow faintly and also come in a variety of brighter colors. Hands come with three digits and a thumb while their feet don't come with any digits, having a very boot-like appearance.

Lore-wise, for tabletop roleplay purposes, knights normally live near canyons, mountainous areas, caverns, and deserts and are very in-tune with the element of earth and have a few racial spells unique to them revolving around said element as well as some healing and support. They're hardy, able to resist sickness, poisons, and exhaustion easily, but they aren't very dexterous and usually fumble with delicate work that requires nimble hands. Knights are usually loyal and fearless and can be quick to make allies with if they share a common goal. Regarding classes, Knights are commonly known to be Fighters, Barbarians, Clerics and sometimes Wizards, while other classes are more rarely seen.

Interesting stuff. I like the cohesion of the world elements and its races. Simple to understand

I noticed you changed from calling them 'wardens' to 'knights' in there. Is it an interchangeable name or simply a mistake from copying?

Thanks, I always try for simplicity~

And yeah, "knights" is their original name as they were created for tabletop roleplay, Pathfinder specifically. "Warden" is what they go by in the Knight & Rogue universe as the main character's name is Knight while also in a setting where there are human knights in armor. So that change was simply made to help prevent confusion, but otherwise the name is indeed interchangeable.

Their true name would be something in the Terran language which would roughly translate to "Vessels of Earth."

Are the elves nice or the usual snooty types? :O

Elves in this universe are intelligent, but also very airy, somewhat ditzy, and even awkward. They love to learn about people they meet for the first time, and engage in small chit chats to heavy subjects. They can be very blunt without any intention of being rude and are in fact rather friendly to the other races, with Fawnae being the only ones they tend to quarrel with. They can be a bit snarky if need be.
They highly enjoy the outdoors, animals, and whatnot, and should they ever hunt the wildlife, they follow rituals to thank those that made the hunt possible. The other races tend to think their methods are an inconvenience at times, but overall, elves are alright to be around.

They sound a lot nicer than most other elves Including the original Norse mythology ones and the Eldar [aka space elves] who basically saw other peoples as stupid savages. :O