The chi-rho is a Christian symbol popularized by the Emperor Constantine. It consists of the first two (Greek) letters of Christos, conjoined into a monogram. Though found in period art – the illustration is taken from a 4th C. coin – the chi-rho does not appear to have been used in period heraldry. See also cross, cypher charges.
Basilius Phocas bears: Gules, a chi-rho argent within an orle of bezants.
Artus Quintus bears: Argent, a chi-rho and a bordure gules.
Konstantinos of Rath an Oir bears: Purpure, a chi-rho and a chief Or.