A journal I guess

Evolution of Them throughout the ages.

Sources: 

https://para.wiki/w/Fleshgait

https://www.reddit.com/r/fleshgait/comments/ongpcv/what_are_fleshgaits_and_what_arent_theory_based/

https://paranormalauthority.com/fleshgait/

2. Crawlers. 

Described as tall, thin, and pale humanoids who sometimes walk on hind legs, Crawlers are famous for their sharp teeth, claws and aggressive behavior. These creatures are usually found in enclosed spaces like caves, and aren't known to attack humans, although they let out an ear-piercing screech when approached. 

This description matches both The Rake and the Fleshgaits, which again leads me to believe they are the same creature. 

Sources: 

https://para.wiki/w/Crawler

https://nationalcryptidsociety.org/2018/04/08/the-pale-crawler-large-grey-crawling-humanoid-in-effingham-illinois/

https://www.reddit.com/r/Thetruthishere/comments/udlpoe/phenomenon_known_as_the_crawler/

https://www.youtube.com/watch?v=6VDGY1kfG0k

https://www.youtube.com/watch?v=OVMZhjXI5rA

This list is incomplete and will be continued.

Now, moving on to Slenderman. 

1. Walking Sam. 

Known in the Oglala Dakota Tribe as the suicide spirit, this notorious creature is believed to be the cause of over 100 teen suicides. He is known only to target younger people, presumably because they are more susceptible and easily influenced. Walking Sam is described as 7 feet tall and with no facial features except his eyes. It's said that he whispers to young people and makes them believe in their worthlessness, encouraging them to kill themselves. Many compare this entity to Slenderman, although this legend has existed among the tribe long before the internet. 

Since most people compare Walking Sam to Slenderman, I don't think you need an explanation as to why I think they're the same creature. 

Sources: 

https://www.ranker.com/list/south-dakota-walking-sam-suicides/laura-allan

https://www.dailydot.com/irl/walking-sam-myth-lakota-pine-ridge-suicides/

https://horrorhubmarketplace.com/legends/the-legend-of-walking-sam/

2. The Hat Man/The Shadow Man. 

Usually a sleep paralysis monster, this tall entity, often seen with a hat upon his head, creeps in at night during sleep paralysis and scares the unsuspecting sleepers. The appearance of this entity differs on a case to case basis, some describing him as malicious and some harmless.  The most distinct characteristic of this entity is how it seems to only watch silently, unmoving, for most of the encounters. In individual cases, some even describe the Hat Man having a long black coat, cane, or pocket watch to complete his outfit. But, this creature doesn't only appear during sleep paralysis. Some witnesses recount seeing him while awake and active, usually after an extreme traumatic or emotional event.

From the description of Hat Man's behavior and appearance, we can conclude that Slenderman and Hat Man are the same creature. Slenderman and Hat Man are both said to stare silently at you, and are known to dress very proper.

Sources:

https://mysteriousuniverse.org/2014/12/beware-of-the-hat-man/

https://mysteriousuniverse.org/2012/09/an-encounter-with-the-hat-man/