Cortical Borers are a Random Event, that creates a disgusting little brain slug and automatically pulls a Ghost/Observer into it, provided their Respawnability set to "yes".
You begin in a random location on the station, with no chemicals inside you, and are very likely to die to the first Assistant that spots you. Your survival rests on finding a Host and seeking refuge inside them.
But, before you start controlling your poor, randomly chosen crew member, you should know the MOST important thing of being a Cortical Borer: your objective is always to survive, and this means to BE ALIVE AT THE END OF THE SHIFT, not kill everyone that stands in your way just because you're an antagonist, or deliberately harm your own Host for no good reason.
Being A Disgusting Brain Slug!
First of all, you should check who your fellow Borers are, and where they are at. You have access to your own Hivemind, which you can speak into by going into IC tab, and setting default language to cortical link. This will let you know if your fellow Borers have infested someone important.
Your main objective is to locate a Host and wriggle into their ear. Once you've done that, you'll be stuck inside their head unless you intentionally release yourself or get surgically removed. You can speak and whisper to your Host, who will now know they have a brain-controlling parasite inside their head. Usually, this does not end well.
Try to be kind with your Host and they will help you survive in even the direst of situations. Remember, you're incredibly fragile when not in a Host, so getting your Host to cooperate with you is paramount. Engage in talks with them, don't take over unless you really have to or if they allow you to, and always remember to use the beneficial chemicals to help them in their personal ventures (see below).
Do be warned, however, that you can easily overdose your Host on Meth, slowly killing them off with Brain and Toxin damage, so try not to use it too much. Deliberately releasing Meth because your Host refuses to cooperate should be avoided. You're not meant to murder every Host who disobeys you.
You generate Chemicals automatically when inside a Host. Your current Chemicals can be found in your Status tab. These can be used to secrete chemicals, or reproduce. Do keep in mind, reproducing can only be done when in full control of a Host (see below), so try and get them to cooperate before you do it, unless you're just brute forcing it. Newborn Borers will automatically pull a Ghost/Observer into them. If none are available, they will remain inert.
Chemicals regenerate rather slowly, so keeping on your Host's good graces is always a good idea.
As a final note, remember that you are very vulnerable to sugar. If your Host consumes anything with sugar in it, you will enter a docile state, and will be unable to do anything. So if you see your Host gobbling down Twinkies, then it's a great time to start running.
You're Mine, Now!
These abilities deal with OH GOD A MIND SLUG GET IT O-Oh, was I screaming? I'm sorry, I had a lucid dream...
|Assume Control||N/A||N/A||~30||This allows you to take direct control of the person you're inside of. Be aware, the person can resist and break this control (anyone with a Medical HUD can identify the person as being controlled, however, as long as you're in direct control)|
|Crawl Through Vent||N/A||N/A||N/A||This allows you to enter the piping system by Alt+Clicking a vent (leads you to the Supply Loop) or scrubber (leads you to the Waste Loop)|
|Dominate Victim||~30||N/A||N/A||Paralyzes a victim for about 3-4 seconds. Be careful, however, because this is not quite long enough to infest them. Either do it strategically at choke points or when they stop and you are hidden.|
|Hide||N/A||N/A||N/A||Hide under tables and lay in wait to slither into an unsuspecting head!|
|Infest||N/A||N/A||5||This allows you to slither into someone's ear and be inside their brain, from where you have access to further abilities. Both you and the Host must remain still during the process, or it will fail. Health Analyzers and Full Body Scanners can still detect your presence, however.|
|Release Control||N/A||N/A||~10||Gives the Host control over their body again.|
|Release Host||N/A||N/A||~30||This disconnects you from the brain and drops you out of the Host's ear to slither away.|
|Reproduce (only available when Assume Control is active)||N/A||100||N/A||Creates a new Cortical Borer at your current location. Be careful about where you do this, as your Host will vomit quite noticeably. Be sure to use it where your newborn child can quickly crawl under cover or into a vent.|
|Secrete Chemicals||N/A||30||N/A||Injects one of 9 possible chemicals (see below)|
|Secrete Mannitol||N/A||30||N/A||Lessens damage to neurological tissue, effective even after catastrophic injury. Used for treating brain damage. You'll want to secrete this after either assuming direct control, or secreting methamphetamine, assuming you want to take good care of your host - both of those actions will cause harm to your host's brain, which is both dangerous for them and will make it harder for you to assume control later.|
|Secrete Hydrocodone||N/A||30||N/A||An analgesic which completely numbs pain. Good for getting your host up on their feet when suffering enough agony to down an elephant.|
|Secrete Methamphetamine||N/A||30||N/A||A highly effective, long lasting muscle stimulant. It allows greater freedom of movement in bulky clothing although it has the side effect of causing some twitching. Using this ability while there's still meth in their system will addict your host, which, while not immediately lethal, will be inconvenient, so be careful.|
|Secrete Saline-Glucose Solution||N/A||30||N/A||A simple chemical that will heal some amount of brute and burn damage, as well as somewhat help in replenishing blood.|
|Secrete Mitocholide||N/A||30||N/A||An advanced medicine capable of healing someone's organs without the need for surgery. Important if your host bursts their lungs, or is in some other way with damaged organs.|
|Secrete Charcoal||N/A||30||N/A||A basic anti-toxin that will slowly remove all other chemicals from your host's body. Mostly useful for if your host is poisoned, but if your host is uncooperative and attempts to sedate you with sugar, you might just be able to give yourself a second wind with this.|
|Secrete Salbutamol||N/A||30||N/A||A medicine that will help your host oxygenate their blood supply - use this if they're suffocating for some reason, or otherwise unable to breathe for themself.|
|Secrete Capulettium Plus||N/A||30||N/A||A form of "poison" that will simultaneously make your host appear dead, as well as render them unable to speak. Useful if you either need them to hide from people, or if you want them to keep quiet for a little.|
|Secrete Spaceacillin||N/A||30||N/A||An anti-biotic that will both ward off viruses in their early stages, and bacterial infections from untreated wounds. Useful if your host needs to undergo emergency surgery, are amidst the early stages of a viral outbreak, or need to make sure that a wound won't get infected, and thus require a trip to medbay, which just MIGHT be dangerous for you, depending on the crew's disposition towards you.|
|Torment Host (only available when Assume Control is active)||N/A||N/A||N/A||Is your host displeasing you? TORMENT THEM WITH LANCES OF PAIN TO THE BRAIN!! (Your host will receive a large message about feeling intense pain. No actual mechanical effect)|
Fight Against Your Mind!
So you have a disgusting little brain slug inside your head. Woe is you.
But wait! Don't just throw yourself out the nearest airlock or commit suicide! Not only will that permanently remove you from the round, but there's a lot of stuff you can do as a Host of a Cortical Borer.
You can try to rationalize with the disgusting little thing and set boundaries. Try to have a nice dialogue and see if you can't benefit off one another. Or just eat a ton of Twinkies and have someone remove the thing from your head so you can squish it.
Remember, it isn't always so bad having a creature that can help you out when in need of a massive power up (that will probably save your ass) or emergency medication. All it asks in return is for you to occasionally puke out some baby slugs. That's not so bad, is it?
If the slug is behaving badly, show it who the boss is and eat some Sugar (simplest way is to gorge on Twinkies, or get the Chef to just let you hit the bottle). It will put the Borer to sleep for some time, which can be used either as a disciplinary method, or as an opportunity to surgically remove it.
Remember, your RP experience may vary depending on how you and it feel like behaving. Above all, try to make it fun for both parties.