The diagonal bar from bottom left to top right of a shield is a ‘bend sinister’, which often denoted illegitimacy. One monarch who made use of the bend sinister was Charles II – for the five children by his mistress Barbara Palmer. All of them also went by the name Fitzroy, meaning ‘son of the King’, another way of proclaiming Royal parentage. Henry Fitzroy, the present Duke of Grafton, is descended from one of them and still uses the baton sinister (a ‘baton’ is like a ‘bend’, but doesn’t go all the way to the edge of the shield) on his arms. The bend sinister as a mark of illegitimacy was rarely used outside the Royal family, though some historical fiction (following Sir Walter Scott’s lead) has suggested it was.
Badly behaved knights could have blood red or orange ‘abatements’ added to their coat of arms. These colours, not used in heraldry for other purposes, were known as ‘stains’ (from which we get the expression ‘a stain on one’s character’). It wasn’t compulsory to wear your coat of arms and shamed knights probably wouldn't have bothered. Nobles executed for treason were made to wear tunics with their coats of arms upside down.
Every poem is a coat of arms. It must be deciphered. How much blood, how many tears in exchange for these axes, these unicorns, these torches, these seedlings of stars and these fields of blue!
The coat-of-arms of the human race ought to consist of a man with an axe on his shoulder proceeding toward a grindstone.