【Fictitious】 , 【fabulous】 ,  【legendary】 ,  【mythical】 ,  【apocryphal】  mean having the character of something invented or imagined as opposed to something true or genuine.

【Fictitious】 commonly implies fabrication and, therefore, more often suggests artificiality or contrivance than intent to deceive or deliberate falsification.

In an extended sense 【fictitious】 definitely connotes falseness when applied to value, worth, or significance and suggests its determination by other than the right standards.

【Fabulous】 stresses the marvelousness or incredibility of what is so described; only at times, however, does the adjective imply a thing’s impossibility or nonexistence. Often it is little more than a vague intensive.

【Legendary】 usually suggests popular tradition and popular susceptibility to elaboration of details or distortion of historical facts as the basis for a thing’s 【fictitious】 or 【fabulous】 character.

【Mythical】 , like  【legendary】 , usually presupposes the working of the popular imagination, but it distinctively implies a purely fanciful explanation of facts or the creation of purely imaginary beings and events especially in accounting for natural phenomena. Therefore,  【mythical】  in its wider use is nearly equivalent to imaginary and implies nonexistence.

【Apocryphal】 typically attributes dubiety to the source of something (as a story or account) and especially suggests that the source is other than it is believed or claimed to be.

In such use it does not necessarily imply that the matter is in itself untrue, but it stresses the lack of a known responsible source. Sometimes, however, 【apocryphal】 loses its stress on source and then may imply dubiety or inaccuracy of the thing itself.