When to use a definite article and preposition together with ‘myriad’

Of the many things we do- then end up breaking the myriad rules of grammar- is ignore the order of sentence construction as prescribed in the English language. This order demands that the subject precedes the verb and object, abbreviated as SVO (Subject +Verb+ Object). 

In some instances, the order is inverted to begin with the verb, followed by the subject. Before discussing this, however, let us briefly take a look at the word ‘myriad’ as used above. Often, we come across sentences like ‘He encountered a myriad of problems in his endeavour’. There are those who take this to be grammatically wrong, but others differ.