From their website:
"In Central European folklore, Krampus is a horned, anthropomorphic figure described as "half-goat, half-demon", who, during the Christmas season, punishes children who have misbehaved. Part of the Series 4 Horror line-up, Krampus features beautifully sculpted details and a fun hidden detail on the reverse side of the mug."
The hidden detail appears to be a pair of hands creeping over the side of Krampus's basket as a victim (child, probably) tries to escape.
Glazed in green (some selective spots wipe glazed to show white) with red interior.