How would one run mimics with poisons.

Mimics that do the poisoning?  Or mimics that get poisoned?

For mimics that do the poisoning, either have them use poison like a rogue would, or naturally produce a poison with a DC based on the Mimic's Constitution.

For mimic's that get poisoned: they usually don't have resistance to poison or immunity to the poisoned condition, so poison works against them as normal.

I mean covering a mimic acting a weapon with injury poison or my old reliable a group of wizards are making super mimics from dragon breath to purple worm levels of poison or something.

If its an injury poison, coating the mimic in it wouldn't likely harm the mimic, since the poison is merely coating its body rather than being injected into it, which is a key mechanic for how an injury poison functions.  A contact poison, though, is a different story.  The mimic would be affected as usual.

I think my favourite mimic application that I’ve seen was in a Team Four Star stream. The party came across a mad wizard’s lab deep inside a dungeon, where they discovered that he had turned his party into various mimics, and they had stayed in the room for hundreds, if not thousands of years.

The party befriended the mimics, and because they were ex-sentient beings, would converse with the PCs and advise them (as they had picked up all sorts of knowledge from the wizard over the centuries), but only if fed. From memory, there was a ring mimic that ate fingers but would then produce a single-use skeleton key per finger, a scabbard mimic that ate swords, etc. eventually they found a ship mimic (that might have been the wizard in the end) that agreed to ferry them around the world in return for wood and other ships to eat. 

I always thought the finger-eating ring mimic was an interesting idea. 

I'm planning to use a hat mimic in my campaign that stays disguised as a hat until the player is on his/her own. They got the hat in the first session and I plan to let them wear it for as long as it takes.

This thread is unkillable. It keeps changing shape but never truly dies. 

P.S. I'm pretty sure that this thread contains more information on mimics than the PHB

Quote from XorianAeravel >>

This thread is unkillable. It keeps changing shape but never truly dies. 

P.S. I'm pretty sure that this thread contains more information on mimics than the PHB

 Not hard, given that the PHB doesn't even mention mimics. The monster manual has four paragraphs and one stat block, so also not hard to beat. Dragon Magazine 75, in the Ecology of the Mimic, manages a full page of information.

Quote from Pantagruel666 >>

Quote from XorianAeravel >>

This thread is unkillable. It keeps changing shape but never truly dies. 

P.S. I'm pretty sure that this thread contains more information on mimics than the PHB

 Not hard, given that the PHB doesn't even mention mimics. The monster manual has four paragraphs and one stat block, so also not hard to beat. Dragon Magazine 75, in the Ecology of the Mimic, manages a full page of information.

 Whoops! I meant to say MM.

Anyway, the OP has done an amazing job on this. Before I saw this thread, I didn't even think of using mimics in my campaign, now I definitely will. 

P.S. Has anyone gotten all the stat blocks and info onto a single doc? Some of the stat blocks aren't directly accessible from this thread so it's slightly confusing.

That article can be found and read HERE, for those who are interested.

I have to give a plug to 2-minute Tabletop for this lovely idea: Mimics swallowed (and your players!) within a gargantuan house-sized and mansion-sized mimic!

https://2minutetabletop.com/5e-encounter-building-fragile-mimics/

 *shrug*

They aren't the first to have thought of the idea.  I'm certainly not, and this thread precedes their post by over two years.

Quote from XorianAeravel >>

This thread is unkillable. It keeps changing shape but never truly dies. 

P.S. I'm pretty sure that this thread contains more information on mimics than the PHB

 Which begs the question, is this thread a mimic?

XD *rolls initiative if the mimic is hostile so I can calm it down*

Have anyone made this into a PDF book? Because it really should be done. This is an amazing resource!

2112MX was working on one, but clicking on the link, it doesn't seem to be available anymore. 

Quote from 2112MX >>

i have it as a WIP on a site called GM Binder

here is the view link

https://www.gmbinder.com/share/-M9wK4pGFJzUapZaGtil

i am working on chapter 2

 Anyone is free to compile what's here and make one on the condition that they don't use it in a for-profit publication.  All the mimics I've posted in this thread are published here on D&D Beyond.  Just put my username in as the author and search for "mimic".

This may be asking a lot, but can you put upload this as a homebrew magic item (also the race, monsters, and such)? And include links? If this is too much to ask, it’s completely fine, and I can make my own (with your permission)

I would also if I shared it, include a link to this (again, with your permission).

edit: can the mimicromicon be used as a spell book?

Almost all the mimics I have posted in this thread have been published here on D&D beyond.  If you search in the homebrew section and put my user name as the author and search for the word "mimic", they should all come back as the result.  As a shortcut, you can click the links following "My Homebrews:" in my signature block, which executes searches with my username already filled in.

You can share the links as you see fit.  No credit is required, but no mimic I've published can be used for commercial projects.  They are free to use, and shall remain so.

As far as the Mimicromicon being used as a spell book: I don't see any reason why not.  As long as the DM is fine with it, anything goes.