I really like the presentation of Psionic rules in Big Dragon’s PX1. In my own games I have added a couple of Powers taken from the Second Edition Complete Psionics Handbook that allow Psychic Monk characters to better emulate the Mystic class from BECMI. In my campaign that is behind the Webcomic, I have replaced the Mystic class with the Monk class from PX1. I previously used other rules, but I like Big Dragon’s presentation so well, I’m just using them as-is with these few adjustments.

Mystara doesn’t really have Psionics in the core setting, but if there’s ever a Mind Flayer I really want it to be the Psionic version. So in my interpretation of the setting, Mystics that are psionic are exotic travelers from distant lands. Additionally, I’m considering The Church of Benekander promoting psionics, since one of Benekander’s precepts is to fight against the influence of Immortals, and the power of psionics comes from within and doesn’t need an Immortal or the Radiance to work. So I have the rules to explore that set. Still need to build it out into how it will work with Mass Combat. Here is what I have so far.

Psychometabolic Minor Devotions

Scale Body
Range: 0 (psionicist only)
Duration: 2 turns
Area of Effect: Personal
The psionicist can selectively expand or shrink his own body proportions in any dimension: height, length, width, or thickness. He can increase or reduce any or all of these proportions by 50% of their original size per round. Maximum expansion is four times original size. Minimum reduction is 25% of the original size.
This power has no effect on clothing or equipment. Ability scores don’t increase either. In other words, the character does not grow stronger simply because he became taller.

Adrenalized Metabolism
Range: 0 (psionicist only)
Duration: 3 turns
Are of Effect: Personal
The psionicist can speed up their metabolism allowing them to act as if under the effects of the Haste spell. The psionicist may move at up to twice normal speed and make double the normal number of missile or hand-to-hand attacks while the devotion is in effect.
This power does not affect the rate at which magic works, so the psionicist cannot use magical devices (such as weapons with additional magical effects) any quicker.