Halaster's blacksphere

Halaster's blacksphere was an evocation spell that enveloped an area in a sphere of force that trapped anything caught within. It was developed by the "Mad Mage" of the Undermountain, Halaster Blackcloak.

Effects
Upon casting this spell, the blacksphere appeared in an area within approximately 250' (76.2 m) of the caster. Comprised of pure force energy, the sphere appeared black as night and had a radius of 10' (3 m). Unless they successfully dodged the spell, any creature caught inside was trapped for the duration of the spell. They could only escape by any means that pierced or otherwise bypassed a wall of force.

The sphere lasted for over a minute, and extended longer depending on the skill and experience of the caster.

Usage
This spell could be used in lieu of wall of force in the creation of beads of force.

Components
In addition to verbal and somatic components, this spell required a lump of charcoal and small piece of onyx.