Creeping doom

Creeping doom was a conjuration spell that called into being a carpet of insects that attacked selected targets.

Effects
Early versions of this spell summoned 500 to 1,000 poisonous spiders, scorpions, beetles, and centipedes that swarmed over a 20 ft (6.1 m) square area. The later version of this spell summoned up to ten swarms of centipedes, each of which could be commanded independently. A swarm could attack any creature that could be damaged by normal weapons and quickly kill them by sheer numbers even though each bug did minimum damage. Swarms could be directed to move, killing anything in their path. If a swarm got too far away from the caster, the early version started to lose bugs,  whereas the later version just stopped moving and attacked any creatures in its area.

Components
This spell required only verbal and somatic components to cast.