I know, I know. This isn't the OSR and/or 5e content you came to expect from me. That'll come too, one day. But I actually did something else I'm actually a little proud of and so I'm going to post about it. I'm sure I'll have more old-school content at some point.
I've been looking for an Animorphs system for a long time.
This weekend it struck me, and I feel stupid for not thinking of it sooner. The answer was staring me in the face all along... Don't Rest Your Head. Powers, terror, insanity, the constant risk of everything turning pear-shaped, it's got everything an Animorphs RPG needs! So I brought what I had worked out myself to my brother for refinement and together this is what we settled upon.
Creating a character
You are an Animorph-- an adolescent given the power to acquire the DNA of living creatures by touch and transform into them. You have been given this power because you were in the mother of all wrong places at the mother of all wrong times and learned a terrible truth: The Earth is being subjected to a secret invasion and help may be months or years away from coming. A dying alien broke the law of his people to warn you and grant you this one weapon, and then he was gone. Whether or not you fully appreciated what this encounter meant, you and a scant handful of others found yourselves thrust into a guerrilla war with the fate of your entire world hanging in the balance.
Why do you fight?
This is the equivalent to the base game's "What's been keeping you awake?" and to a lesser extent "What just happened to you?" Your character has just become privy to an awful secret and drafted into a war for humanity's survival. What will motivate them to keep going through the horror and insanity?
Think about it: Is there someone you love that has already been made into a Controller, or someone you'd risk life, limb, and sanity to protect from enslavement at the hands of the Yeerks? Is this war a choice for you, or an obligation? Does fighting the Yeerks have something to offer you apart from mere survival?
What's on the surface?
What lies beneath?
These two are both essentially the same as in the base game, and are important for the same reasons.
Who else in the group do you have history with?
Now that you have some idea of who your character is and who the other PCs are, it's time to draw some connections between you. This is another question that takes some elements from the base game's "What just happened to you?"
Think about it: Are you friends with any of the others? Are some of them more or less strangers to you? Is there one whom you resent or distrust? Conversely, is there one you're especially close to? What happened in your past to cause that relationship? Why were you all together in an abandoned construction site of all places?
What won't you sacrifice?
In a sense, this is the closest to the base game's "What's your path?" That question doesn't necessarily fit this game, though-- you've already explored your goals. This is a time to look at your fears and your boundaries instead.
Think about it: What are your character's most sacred principles? What would it take to bend or break them? What would your character do to survive? What would they do to win? What are you prepared to lose?
Dice and Coins
The pools in Don't Yeerk Your Head are a little different from those of the base game. Don't choose a Madness/Stress talent, your talent is Morphing. While you are morphed, the natural abilities of your form (anything from an elephant's size and strength to the host of a high-ranking Yeerk's ability to be recognized by their subordinates) is an Exhaustion/Time talent
Discipline remains mostly the same. If Discipline dominates, things stay in control.
Exhaustion becomes Time. If Time dominates, what you are doing takes more time and effort than you expected. Whenever a PC's time score increases beyond 6, they are Running Out Of Time. When a PC is running out of time, all their response boxes clear out and their time dice clear away. If they are in morph, most likely they are now a nothlit, trapped forever in their current form. Running out of time may also mean they are dying or in immediate danger of death, or are otherwise in an extremely critical fix.
Madness becomes Stress. If Stress dominates the situation places a great deal of psychological strain on the PC. If they are in morph, especially a morph they are unusued to, their response will likely take the form of being overtaken temporarily by the natural instincts of their new form, but it could also be social or otherwise non-literal-- a Fight response could mean you're standoffish and confrontational, a flight response could mean you're withdrawn and brooding. If no more response boxes are available, the PC Undergoes Trauma. When a PC undergoes trauma, all their response boxes clear out and they gain a permanent stress die but lose a discipline die. If a PC's discipline score reaches zero, things come to a head. They may give up the fight entirely, take reckless actions without regard for their own safety or that of the team, succumb to sheer bloodlust, or otherwise make themselves a liability, threat, or simply a low-functioning wreck. Either way, they're out of the picture, probably for good.
Pain is much the same as ever. If Pain dominates, either failure comes for free or success comes at a dear price.
Despair and Hope are more or less the same as in the base game.