Charlemagne's father, Pepin the Short, held a council there that brought together the Frankish leaders and religious figures for some political management followed by religious matters. Among other things, this first Council of Attigny made a decree pro causa religionis et salute animarum" ("for the sake of religion and the salvation of souls") that all who signed (several bishops and abbots) would pledge to sing a certain number of psalms (usually 100) and/or celebrate a certain number of masses for the soul of any of the signees who died.
In 822, Pope Paschal I convened the Second Council of Attigny, partially for the purpose of dealing with Louis the Pious. (Paschal also wanted to confirm some rules from 816 about the conduct of canons and monks.) Louis was Charlemagne's son and successor, and had done his best to eliminate any potential opposition to his rule by dealing with his relatives, sometimes very harshly. Some he simply tonsured and sent to monasteries, such as his younger brothers Hugh, Drogo, and Theodoric. His nephew, Bernard of Italy, however, had a worse fate.
Bernard feared that Louis would take Italy from him. Fearing rebellion, Louis captured Bernard and intended to blind him, but the process went too far and Bernard died. This was not acceptable behavior from the man who was Holy Roman Emperor. Louis was made to apologize in public for the treatment of his brothers, and perform public penance for the death of Bernard. (You see an illustration of the penance above.)
Louis also reconciled with his brothers. Hugh was made abbot of St-Quentin, and Drogo was named Bishop of Metz. Some of the co-conspirators of Bernard were released from monastic confinement and allowed to take positions at court. Louis also confessed to offenses that would not ordinarily have been significant offenses by a ruler, but he was, in fact, a pious man who cared about the church and his soul as well as his secular power.
Louis ruled for almost another two decades, with a couple civil wars and several other notable events, but tomorrow I will go back to the Council of Aachen of 816 and the attempt to regulate monasteries and the relationship of church property to the king in whose territories they lay.