Abstract We exploit the 6D. N $$ \mathcal{N} $$ = (1. 0) and N $$ \mathcal{N} $$ = (1. 1) harmonic superspace approaches to construct the full set of the maximally supersymmetric on-shell invariants of the canonical dimension d = 12 in 6D. https://www.roneverhart.com/Cleglaw-s-Tooth-West-Ladder/