Inventing
The Designing Phase
When a character turns an idea into plans—be they architectural blueprints, a new spell, an artificed item, or a poison—they attempt to produce a number of eureka's: insights that count toward completing the Design Phase.
Gaining a Eureka. While taking a short or long rest, a character may spend one uninterrupted hour in deep study and planning to attempt a Eureka Roll. A short rest permits one roll; during a long rest a character may make at most two Eureka Rolls (two hours total). Each roll requires the hour be free of interruption and solely devoted to the design task.
Eureka Roll. Make a Eureka Roll (d20) for each hour of concentration. There are no critical failures. A failed roll simply yields no progress; a successful roll yields a Eureka moment as follows:
| Result | Eurekas gained |
|---|---|
| 1-9 | none |
| 10-19 | one |
| 20 | two |
Note to DMs
The DM may grant advantage or impose disadvantage on the roll for circumstances that significantly aid or hinder study (access to libraries, mentors, labs, interruptions, illness, magical aid, etc.).
Design Requirements. Each design requires a number of successful Eureka Rolls to complete; the DM determines the requirement for any particular spell, item, or concoction. When the required Eurekas are accumulated, the design phase is complete and the project advances to the construction or synthesis phase as the DM decides.
Note to DMs
Use Eurekas to pace research and reward invested downtime. Grant research bonuses (reduced requirements, advantage, or extra progress) when PCs secure exceptional resources or mentors; likewise, make prolonged study a source of complication or rivalry when appropriate.
Generally designing new items follows the same Eureka system. However, there are some optional rules that you can adopt for different types of items; specifically, poisons, spells, ...
Alternate rule: Collaboration
The DM may rule that Eurekas may be pooled among collaborators.
Inventing: Spells
The complexity of creating new spells is very complex. Only masterful mages can start to create new spells. In the table below we provide suggested minimum level character and amount of Eureka's for different levels of spells.
| Complexity | Typical Examples | Suggested EUREKAs | Suggested level |
|---|---|---|---|
| Low | Cantrips, common consumables | 3 (1+1d4) | 8 |
| Moderate | 1st–2nd level spells, common alchemical recipes | 7 (2+2d4) | 11 |
| High | 3rd–5th level spells, uncommon → rare items | 11 (4+3d4) | 15 |
| Extreme | 6th–8th level spells, rare items, complex constructs | 16 (9+3d4) | 18 |
| Legendary | 9th-level spells, legendary items | 30 (16+4d6) | 20 |
For example, a dungeon master may sets a new 3rd‑level spell at 8 Eurekas. A lone wizard on a long rest may make two Eureka rolls that rest, gaining 0–4 Eurekas depending on the results.
Inventing: Poisons
Inventing poisons is a far more varied discipline. Attempted by both amateurs, master poisoners, and mages. Subsequently, the range of difficulty is much larger.
Construction phase: Spells
Construction phase: Magic Items
Construction phase: Poisons
Basically the brewing phase described in the [Poison Manual](./index.md
Construction phase: Weapons
Integrate: Weapon Customisation for an easy non-magical level of invention require at most 2 Eurekas.