The aircraft was descending in icing conditions with the engine anti-icing system selected ON. A loud bang was heard from the right engine and the aircraft yawed to the right with an associated reduction in torque. The right ignition light illuminated followed by right engine re-light with subsequent normal engine operation. The descent continued for an uneventful landing. Investigation found one compressor blade bent. The blade was dressed in accordance with approved procedures. A subsequent ground test determined the engine anti-icing system was serviceable. It is likely that ice ingestion resulted in a short term power 'rollback' coupled with minor compressor blade damage. Power was restored by the normal functioning of the auto-ignition system.