Having lived so very long that your mind and body have begun to decay though you yet live,  your spellcasting can unleash surges of untamed magic. Once per turn, the DM can have you roll a d20 immediately after you cast a spell of 1st level or higher. If you roll a 1, roll on the Warlock Wild Magic Surge table to create a magical effect. If that effect is a spell which normally requires concentration, it doesn't require concentration in this case; the spell lasts for its full duration.