What is it?

Mythras Encounter Generator is a tool that allows gamemasters to quickly define, maintain and generate groups of NPC's and monsters.

Creating new templates

If you don't find the NPC/monster you need from the list of existing templates, you can create the template yourself (login required). Use the My Content -page to manage and create your templates. You can also create your own parties (collections of enemies).

A word on die formulas

The program makes extensive use of die formulas. The theory behind this is simple. The standard 3D6 roll yields an average value of 10-11. The minimum roll is 3, the maximum roll is 18. The distribution of values is a bell curve: the average results will appear much more often than the extremes. If you want a higher result, you could enter 2D6+6. This yields a minimal 8, average 13, maximum 18. A significant increase. A less brutal improvement could be 3D5 + 3. This yields 6-18, average 12.

The simple way to calculate this is as follows:

  1. The average result of any die is: (min+max)/2.
  2. The average result of any combination of dice is the sum of the averages of the individual dice. So the average of a D6 is 3.5, and the average of 2D6 is 7, the average of 3D6 is 10.5 (hence the 10-11). The average of a D5 is 3.
  3. Whenever you roll more than one dice, the outcome will be a bell curve: extremes are rare, averages are common. When rolling one dice, the result is linear.

So if you want to add 10-20 percentiles to a skill, you can add 1D10+10. This gives a linear result of 11-20. Every result occurs equally often.

If you want a very strong human you can use 2D3+12. This yields an average of 16 and a result beween 14 and 18, with 16 occurring most often, and 14 and 18 most infrequently.

If you want a veteran to have a combat skill with value 60-80, use 60+1D20 for a linear result, or 60+2D10 for a result where 70 is more likely than 62 or 78.

Template editor

Weapon and spell probabilities

Adding weapons and spells to a template both use the same system for selecting which item to add. There are two elements you can modify: Probability of the specific items and the Amount. The Amount tells how many weapons/spells to add from the current category. The Probability describes relative chances for the item to be picked. Items with probability 0 will never be included.

How probability is calculated?

When calculating the probability of a single item, the probabilities of all the items are first added together. The chance of a specific item to be picked is relative to the total.

Example 1: Amount 1; Dagger prob 1; Knife prob 1 (all other weapons have probability 0). One weapon will be selected and it will be either knife or dagger. The total probabilities are 2 (1+1) and the chances for either dagger or knife to be selected are 1/2 (50%).

Example 2: Amount 1; Shortsword prob 1; Battleaxe prob 2; Shortspear prob 3. Out of the three options, one will be picked. The total probability is 6 (1+2+3). The chances for the different options are: Shortsword 1/6 = 17%; Battleaxe 2/6 = 33%; Shortspear 3/6 = 50%.

Example 3: Amount 2; Dagger prob 9999; Shortsword prob 1; Battleaxe prob 2; Shortspear prob 3; Out of the four options, two will be selected. The total probability is 10005 (9999+1+2+3). Dagger will be picked practically always (9999 chances out of 10005 = 99,94%). The second weapon will be picked as per example 2.

Example 4: Amount 1d3+1; Alarm 1, Repair 1, Protection 1, Darkness 1, Ignite 1, Bludgeon 1, Might 1, Shock 1. The generated enemy will have 2-4 spells (1d3+1). Each spell has an equal possibility to be included.

Note! The amounts apply only within the specific categories. For weapons the categories are 1-h melee weapons, 2-h melee weapons, ranged weapons and shields.

Additional features

The generated enemies can have some random and non-random features added to them. To add a random feature, select the feature from the list, click add, and assign a percentile probability. 100 will mean it will always be selected. POW+POW+POW will mean, that there's a POWx3% chance for the feature to be selected. If the feature is added, a random item from the feature list will be added to the enemy. To see the items on the different feature lists, add feature to the template and click 'View items'. (You can remove the feature if you don't want to add it.)

To add a non-random feature, select first the feature list, and then the item from the list. Non-random features (for example Nightvision on Trolls) are always added to the enemy.


All Standard skills and Professional skills work along the same lines: you get the skill name, then a checkbox to indicate whether this skill must be included when generating NPC. Next is the calculation field. Default setting is the skill calculation formula as per the rulebook. In order to make your character more competent you can change these formulas. Athletics starts at STR+DEX. For a skilled warrior, you might want to increase this to STR+DEX+20. You can also use dice variables, so STR+DEX+D20+10 would work too. The final field, Combat Styles, works similarly. Only difference here: it cannot be deselected, and you need to name your combat skill, as described in the rulebook. This can be any name, it's only for flavour.

JSON interface

If you can do a bit of programming and want to format the output yourself, you can read the data in json-format using the url https://mythras.skoll.xyz/generate_enemies_json/?id=<template_id>&amount=<amount>. E.g. https://mythras.skoll.xyz/generate_enemies_json/?id=1778&amount=2. The list of all templates is available at https://mythras.skoll.xyz/index_json/.