The overmind attacks by launching a small nail. It deals DAMAGE. It defends itself by disrupting your concentration with a pinball.
The overmind seems to grant a bonus to rogues based on there level, level1 rogues appear to get a 1 bonus, level2 a 2 bonus and so on.
Instead of attacking or concentrating, the overmind may generate an image of a still-living rogue in the dungeon, which will then move one room towards the room containing the overmind.
As a reaction, the overmind will launch a tiny sphere of metal, forcing a body check against a target of 12. On a failure, your concentration is broken and the attack proceeds. On a success, your concentration remains intact and the attack still proceeds.
Since the overmind is not exactly fearsome in direct combat as Level 4 enemies go, and prefers to concentrate to the maximum before attacking if it attacks at all, it may be a good candidate for attacking early with a relatively weak setup, especially if you can isolate it from reinforcements (eg. with a Rod of the Master Builder) or simply by killing it very rapidly.
Community content is available under CC-BY-SA unless otherwise noted.