Kobold Miners

+18: Smokescreen: Each kobold sets off a demolition charge within five feet of their location. A smoke cloud ten feet wide and fifty feet tall spreads
X: from this area, breaking line of sight. This smoke lasts for one round. Creatures behind this smoke are considered invisible, and attack rolls
X: against them or through the smoke are made with disadvantage. The kobolds are able to teleport between the smoke towers until they disappear.