The World
Skills & Spells
You get better at what you do, not at what you buy. Skills improve by being used, and failing at something still teaches you about it.
Improvement comes from use
Every skill and spell carries a proficiency. Using it can raise that proficiency, and failing can raise it too - the attempt is what teaches, not the outcome. This means the way to get good at picking locks is to pick a lot of locks, badly, until you do not.
Practice takes you part of the way. There is a ceiling on what practice alone can reach, and the last stretch to mastery is earned in the field.
Your class decides your ladder
Classes grant abilities at set levels, and those grants are what make the five classes play differently rather than just look different. A Mage's ladder runs through magic missile, burning hands and fireball; a Fighter's through enhanced damage, a second attack and then a third; a Rogue's through lockpicking and an early riposte.
Skills re-sync against your class every time you log in, so a class that gains a new ability reaches characters that already exist rather than only new ones.
Weapon proficiency is separate
Long blades, short blades, blunt weapons, hammers, staves, axes, thrown weapons, bows and your bare hands each have their own proficiency. Your class starts you off skilled in the weapon it prefers; picking up anything else means learning it the hard way.
Casting is instant, and it costs
There is no cast bar and no interruption window. A spell fires when you type it, spends its mana, and then imposes a delay before you can act again - so a "slow" spell is one that leaves you standing there afterwards. Running out of mana mid-fight is a mage's real death sentence, not a slider to manage.
Anything can be scripted
Skills and spells can carry Lua for custom formulas and effects, which is also how quests, NPC behaviour and room events are written. It means an ability can do something genuinely specific rather than being another damage number with a different name.