Insect Cloud

Swarms of flying, blood-drinking bugs infest the Feydark, searching for targets for their hunger. Though they can survive on carrion and plant sap, they greatly prefer living prey.
    An insect cloud can occupy a single square or an area up to 5 squares on a side. It can be identified with a DC 20 Nature check.

    Effect: Insect clouds create lightly obscured terrain. Any living creature that starts its turn in an insect cloud takes 1 damage per tier (or 2 per tier if bloodied).
    An insect cloud changes position during an encounter. Assign the cloud a position in the initiative order (initiative +10) and move it 1d4-1 squares on its turn, typically toward the nearest bloodied combatant.
    Any blast or burst that includes one or more squares occupied by an insect cloud disperses the cloud in the included squares.
    Usage: As it moves about during combat, an insect cloud adds an element of unpredictability to an encounter. Player characters can also take advantage of the situation by moving enemies into the cloud.

Published in Underdark, page(s) 100.