Jesus, Himself, taught that false Christs and false prophets would arise.

..............................And this was particularly associated with the Great Tribulation.

.....................Matthew 24:21. 24-25
"21 For then shall be great tribulation, such as was not since the beginning of the world to this time, no, nor ever shall be.
24 For there shall arise false Christs, and false prophets, and shall shew great signs and wonders; insomuch that, if it were possible, they shall deceive the very elect.
25 Behold, I have told you before."