Making a Split Personality character who can ask the other personality to take over

[TheRealMe]

I would like some help in building a GURPS character with two souls (not quite Split Personality) where each personality can call upon the other to take over the shared body at need. Let us say that the two personalities are a mage and a fighter. If suddenly the mage is engaged by multiple warriors in close combat, she can call upon the fighter to take over their body to defend it. I would also like the idea of the switch happening sometimes under stress. The body will not change its appearance, but its stats, skills, advantages, and disadvantages might be somewhat different.

I have considered the Ally rules, using Frequency of Appearance as the chance that the switch would work. With normal rules, your Ally would be fighting beside you, but in this case as described, the mage effectively disappears when the fighter appears. Since you are losing a person, this seems to be worth less than a normal Ally. On the other hand, you can tailor your response for any situation to whichever character would be more effective. That is to say, the fighter doesn't have to worry about protecting the mage in a physical fight; the mage is no longer present to be a target. Is it a wash, then? Should I use the normal Ally points?

How would the Split Personality disadvantage (or something similar) work with this arrangement? Clearly if you change personalities under stress, but can just call upon your Ally to change back, that will make Split Personality less of a disadvantage. How much less? Does it depend on the chance of successfully calling upon the Ally?

Or is there some other mechanic that would work better? Shapeshifting's Alternate Form?

I realize that Split Personality shouldn't normally change physical aspects of the body and that Alternate Form shouldn't normally change the mental aspects or skills. That is why I originally thought about using Ally rules.

Thank you for any advice.

[Christopher R. Rice]

Use Alternate Form for this. There is an example in GURPS Bio-Tech. See p 180 of that supplement under the modification called "Wetware Sub-Personality."

[sir_pudding]

Originally Posted by Ghostdancer

Use Alternate Form for this. There is an example in GURPS Bio-Tech. See p 180 of that supplement under the modification called "Wetware Sub-Personality."

Also the Loa variant of Alternate Form in GURPS Horror: The Madness Dossier.

[Leynok]

Originally Posted by TheRealMe

I realize that Split Personality shouldn't normally change physical aspects of the body and that Alternate Form shouldn't normally change the mental aspects or skills. That is why I originally thought about using Ally rules.

Alternate Form is the most simple solution, and there is nothing saying that it can't change your mental traits.

Although there is another (much more complicated) way that I've done the same concept. I made an Ally with some custom Enhancements that I worked out with my GM so I could create and control the Ally and then followed the rules suggested here.
http://forums.sjgames.com/showpost.p...86&postcount=8
Only they didn't take the Extra Head Advantage since knocking one out would still knock them both out.