These birds were formerly thought to be forest batises (B. mixta) but in 2006 were described as a new species based on differences in morphology and mitochondrial DNA from those birds in northern Tanzania and Kenya.

The dark batis is about 10 cm (3.9 in) in length and weighs 10–15 g (0.35–0.53 oz).

The female has a greyish crown, brownish back, dark mask, slight white supercilium and a narrow rufous stripe on the wing.

[2] The dark batis has a variety of whistling and harsh churring calls and its wings make a whirring sound in flight.

It forages mainly in the lower and middle levels of trees, feeding on insects such as termites.