Creeping Doom allows the caster to call forth insects to attack the enemies. Invisibility offers no protection against the spread.
In-game description Edit
|“||When the caster utters the spell Creeping Doom, he calls forth a horde of venomous, biting and stinging arachnids, insects, and myriapods. This carpet-like mass swarms over a large area, spreading to all creatures within 30 ft. of the target. Those trapped by the insects suffer 2 points of damage each second and a spell failure rate of 100%. For each round the victim remains inside the cloud, he must make a Save vs. Spell at -2 or run away in fear for one round. The advantage of Creeping Doom over the 5th-level counterpart Insect Plague is that it does twice as much damage in half the amount of time.||”|