Fury of the Immortals
Wild Magic or the Wyrd
Wild Magic Surges, or the "Wyrd" as the denizens of Blackmoor call it, have the potential to affect any Arcane spell caster on Mystara. Generally, they occur most often where there are concentrations of a particular type of unusual, smooth black stones that seem to have small, silvery motes of light trapped within – almost like tiny stars in the night sky. The University of Blackmoor contains several such stones for study and it is said that Blackmoor Town was built over such stones. In Blackmoor, such stones are said to also be concentrated around the Stormkiller Mountains and the Valley of the Ancients. In modern Mystara, magical aberrations have been experienced in and around The Broken Lands and parts of Glantri.
In terms of game mechanics, when in the presence of the Wyrd, a Wild Magic Surge can occur when an Arcane spell is cast above the level of a Cantrip or a magic item charge is expended. A Wild Magic Surge will occur on a roll of 1-2 on a D20. The surge might cause a random, strange occurrence or it might empower the spell with the same effect of either a Careful Spell, Distant Spell, Expanded Spell, Extended Spell or Twinned Spell Sorceror Metamatic effect. The caster will have a chance to make a Arcana check with a DC equal to 15+ the spell level to determine whether they lose control of the spell. Success means they maintain control and the spell is empowered. Failure will result in a Wild Magic effect.
The DM will inform players when a Wild Magic Surge occurs.