Ok can't give you detailed stats on these, more like guidelines.
They look like typical devils 1-2' tall ,dead black in color, they would be very stealthy except for their incessant chattering.
They are a swarm and due to their great speed will surround and swirl around the party getting three attacks against each party member per round for minor damage each attack (poss totaling significant damage total over round). there is a 80% chance per attack that they will work major mischief on 25% of the party instead of damage(switching weapons, pulling down pants , stealing shields etc.) AC should be about chain(even thou they are super fast, they are unarmored and densely packed) Use group HP and make it sugnifigant. at about 60% damage they will all make prank attacks and then run away.
(yes they are based on the MTG card)