This puzzle originated from here.

The initial clue on the website can be decoded with rot20.

The pigpen cipher on https://enigmagamefirstclue.com/ leads us to https://instagram.com/p/B09zEQ8Hs3Q. This in turn tells us to go to the reddit post in the bio of the profile that posted it: http://reddit.com/comments/clehu5.

From there, we look at the other recents posts by that reddit account, and see a lot of empty posts with only a number title. Multiplying those together brings us to https://142449721787899069173907200.com/.

One base64 decode and another substitution cipher later, we go looking for a text file. From the response headers of the site, we can see that it's served by github, so likely to be github pages. Searching for the content of the index page brings us to https://github.com/enigma-number-acct/enigma-number-acct.github.io, and from there, we find 2 text files, one is a columnar transposition cipher pointing towards the other, the other contains the id of a tweet: https://twitter.com/5dd842be9f5c291/status/1160017086472695809.

Solving the templar cipher, and interpreting the hint we take 2*4*6*8*10*12*14*16*18*20 and go to https://www.instagram.com/3715891200_/. Taking the audio from the video posted there, we reverse it and speed it up, resulting in instructions to go to https://100-225-441.com/.

Another base64 step, and decoding decimal to ascii later, we look up the three numbers in the url on oeis, and move on to 784*1296*2025 = https://2057529600.com.

The image we find there takes the cicada3301 approach to hint to the outguess tool, and applying that without password brings us to the next clue.

Following the instructions in that clue, we obtain the final answer: 412097976612917584290000000.