Which 5e rules Nyxfall actually implements
Plenty of AI role-playing tools say "5e compatible" and mean the AI has read about it. Here the mechanics are resolved in code, so this is a list of what genuinely runs — and what does not.
Character and progression
| System | What runs |
|---|---|
| Ability scores | Six scores with modifiers, applied everywhere — attacks, saves, skills, carrying capacity, spell save DC. |
| Races | Racial traits, ability score increases, speed, size, darkvision and innate proficiencies. |
| Classes | Hit dice, proficiencies, saving-throw proficiencies, class features gained by level, and per-class resources. |
| Subclasses | Chosen at the level your class expects, with their own features. |
| Multiclassing | Prerequisites enforced, hit dice by class, proficiency taken from the correct class, and a combined caster level for slot progression. |
| Levelling | Experience thresholds, hit-point gain, proficiency bonus by total level, and feature unlocks. |
| Feats | 73 feats with prerequisites checked against your scores, race, armour proficiency and caster status. Their effects apply at runtime rather than sitting on the sheet as text. |
| Backgrounds | Skill and tool proficiencies, plus personality, bonds and flaws the Dungeon Master reads. |
Combat
| System | What runs |
|---|---|
| Initiative | Rolled, ordered, and tracked across rounds. |
| Action economy | Action, bonus action, reaction and movement, each spent separately. |
| Attacks | Attack rolls against AC, proficiency and ability modifiers, critical hits on a natural 20 and their extra damage dice. |
| Advantage | Advantage and disadvantage from position, conditions, spells and features — and they cancel. |
| Damage types | Thirteen damage types with resistance, immunity and vulnerability applied per creature. |
| Conditions | Fifteen conditions with their real mechanical effects, plus exhaustion levels. |
| Death saves | Dying at 0 hit points, death saving throws, stabilising, and instant death from massive damage. |
| Cover | Half and three-quarters cover adjusting AC and Dexterity saves. |
| Tactical map | Combat plays out on a hex battle map with real distances, movement costs and line of sight. |
Magic
| System | What runs |
|---|---|
| Spell slots | Slots by level and caster type, spent on cast, recovered on the correct rest. Warlock pact slots return on a short rest. |
| Preparation | Prepared and known spells respected per class. |
| Upcasting | Casting at a higher level scales the effect. |
| Concentration | One concentration spell at a time, broken by damage with a Constitution save at the right DC. |
| Saves and attacks | Spell attack bonus and save DC derived from your casting ability, including bonuses from attuned magic items. |
| Rituals | Ritual casting flagged and available where the class allows it. |
| Areas of effect | Cones, cubes, cylinders, lines and spheres resolved against the map. |
Equipment and the world
| System | What runs |
|---|---|
| Inventory | Weight, carrying capacity and encumbrance. Every catalogue item has a weight and a price. |
| Armour | AC by armour type with Dexterity caps, shields, and Strength requirements. |
| Attunement | Three attunement slots, with class and caster requirements checked. |
| Durability | Gear wears through four condition tiers from critical hits taken, natural 1s, and corrosive attackers. Penalties apply, breaking unequips, and repair is a real service. |
| Rests | Short and long rests with hit dice spent, resources recovered, and exhaustion relieved. |
| Food | Rations are items with weight and a shelf life. Days pass, meals are eaten, preserved food travels, fresh food spoils on a date. |
| Travel | Distance, pace, terrain and weather all affect how many in-game days a journey costs. |
| Crafting | Learn a trade, carry the tools, stand at the right bench, and spend real days — eating the whole time. |
| Skill checks | The full skill list against DCs, with proficiency and expertise. |
What is deliberately not here
- Nothing outside the open licence. The mechanics come from the System Reference Document. Material Wizards of the Coast did not licence is not reproduced.
- No lifted prose. Descriptions in this game are written for it.
- No optional-rule sprawl. The aim is a game that runs the core rules correctly rather than one that claims every variant and gets them subtly wrong.