Pieter Pourbus’ Last Supper of 1548 (Bruges, Groeningemuseum) contains some unusual iconographic elements that have not yet been extensively analysed: the figure of Judas, rising from the table and making a move to leave the gathering; the devilish creature entering the room from the right; the boy picking up the overturned chair in the foreground. By making use of recent scholarly insights into the employment of the anthropological concept of ‘liminality’ in the context of the visual arts (notably by Lynn Jacobs on Early and Renaissance Netherlandish painting and manuscript illumination), this contribution aims to show that these features were meant to enhance the contemporary viewer’s involvement in the depiction. The work seems to invite them to enter, as it were, the painted realm and to take Judas’ abandoned place. An investigation of Last Supper imagery in the Western European visual arts from the late Middle Ages and the Renaissance reveals that in some cases the figure of Judas plays a distinctive role in the presentation of the iconography and in the viewer’s devotional and psychological experience of participation in the sacred story. Sometimes, as in a panel from the circle of the Master of the Amsterdam Death of the Virgin (c. 1485-1500) or in the likewise anonymous Antwerp Last Supper (c. 1525-1530), a mortal human has been included in the painting, portrayed in the immediate vicinity of the scene and apparently being ready and prepared to take over Judas’ place once the latter leaves the gathering. Pieter Pourbus’ painting, which probably played a role in the literary-religious context of the Bruges rederijkers’ Chamber of the Holy Spirit, is more inventive in nature. Lacking an intermediary worshipper depicted in the foreground, it transfers this worshipper’s role to the viewer, thus establishing a bridge between the painted realm and the real world.