One very long string, but looks like there are some things repeating themselves.
We will need to divide the string a bit and see what it reveals.

[hint]

After splitting, counting the edges might help you further.

[/hint]

Spoiler

Seeing the words octagon, triangle and line in the text, we could assume that geometric shapes are being references here.
Divide the text up into meaningful geometric shape names. octdecagon octagon line octdecagon pendedecagon enneadecagon icosikaidigon pentagon enneadecagon heptagon triangle enneadecagon icosikaidigon tetrakaidecagon
With the help of Google and Wikipedia, we find this list of polygons.
Replace each polygon with it’s value in the table, except for line, it has 2 “edges”. 18 8 2 18 15 19 22 5 19 7 3 19 22 14

Using the alphabet index of a=0..z=26, we get our pre-/suffixes SICSPTWFTHDTWO 6CSP2 F3D2O

When a code is missing it’s keyword, it generally is the name of either the process or the subject of the substitution.
In this case, we were working with shapes and shape is a known keyword. Subbing that in reveals our full passcode: 6CSP2shapeF3D2O

Code #2

Observations

Only letters in the code, so assume that the numbers will be written out.
The normal ROT/Atbash/Rectangle/Skip doesn’t give any results.

[hint]

When the normal results give nothing, take the next step of “try these automatically first” ciphers.

[/hint]

Spoiler

Using the Autokey Vig cipher with a passphrase of a, we get almost finished result: eijnothmantrayniuseq
Switch out the numbers for our final solve 8jno3mantray9u7q

Code #3

Observations

Here we have a string that has a few letters repeating at the start and others repeating at the end.
Those infront are not all repeated in the second part, hinting at a two sectional code.
We can also semi see very familiar pairs.

[hint]

What happens when you cut in half and fold over?

[/hint]

Spoiler

Make two lines of the entire string fsofznsfnefsfeesfsfeoetfzssensff
ioeiieeeiwiniiiieiioiiiiiiieinii

Reverse only the second line to reveal two letter numbers! fsofznsfnefsfeesfsfeoetfzssensff
iinieiiiiiiioiieiiiiniwieeeiieoi

Reading each columns, write down the numbers. 56150965985648875658182506789745

Making pairs of this shows us that they are not suitable for decimal/hex to text conversion.
But since we already had one reverse in this code today, we see that reversing the numbers gives us the ranges we need. 54798770528185657884658956905165

Pair them up 54 79 87 70 52 81 85 65 78 84 65 89 56 90 51 65

and finally convert from decimal to text for the final solution 6OWF4QUANTAY8Z3A

In addition to the three codes hidden in this post, we also had a Portal clue.
Both factions will always try and figure out what Portal is referred to by such posts and try to get to it first.
Can you determine which Portal this clue is referring to? You will need everything in the post (and subsequent hints posted later) to find this Portal.