Okay so a few things. First off, it's a bitch and a half to get an actual outsider into our world. They're sealed off at the Outer Gates and guarded by the Gatekeeper (and who knows what other reality loving helpers).
Past that, let's say it did work - and don't misunderstand, I'm not saying this concept is good or even that I'd allow it in my games (I wouldn't) but just for theory's sake - so some power in the world is trying to get an outsider here through an architectural spell form. Magic on that level would almost certainly not be point and click but need some power flowing in. Let's say the Caster in question is a dark wizard of some degree who's had the outsider whispering in his mind to slowly drive him insane and thus into doing this stupid ritual.
The Nameless Architect takes the basics of the spellform and maps it out to the point that it's ready to be built. The Dark Wizard is paranoid as fuck of the wardens finding out so he makes sure that no one knows what they're building except the architect (has him sign a confidentiality agreement). I imagine this would make construction a pain but give the Dark Wizard some bonuses to resources and you're good. Money buys complexity. This makes the Nameless Architect a necessary resource as well as a threat to the paranoid Dark Wizard.
When the building is complete the dark wizard now needs to power it. The building will look harmless from the outside, masking the spellform within it. The Dark Wizard will power it with blood and does this through knocking out and tying up the 5 highest ranking people working on the building; the people who knew the most about what it was. This of course includes our hero, the Nameless Architect. Yeah, I'm going to start calling him NA and Dark Wizard DW.
He aligns the 5 people at the 5 corners of the spellform and begins the ritual killing them one by one. The Gatekeeper of course knows about what's going on (though of course not from Chronomancy because that would be illegal >>....) but can't act too directly due to paradox so has the wardens sent in at JUST the right moment to cause the spell to be interrupted in with NA and 1 other left alive. For simplicity's sake let's say they were all awake and gagged, though not blindfolded, before the spell started and NA has been trying to get free.
The spell goes BOOM! This kills the DW and perhaps sends people flying back against walls and the like. NA manages to free his hands, unties his legs and bolts. the Wardens (let's say one cracks his head open and dies or is so close to death that the other can't worry about the bolting prisoner and the still tied up prisoner while saving his brother in arms.
While the Outsider wasn't freed the gateway was opened to him enough to at least send a portion of himself into who would have been the DW but he died so it instead went to NA who had the closest personal connection to the Outsider other than DW because of the personal touches put into the spellform/building. This causes NA to take the power Demonic Co-Pilot.
Over time the Outsider's Image (OI) will tempt him and turn him but probably not "Mark" him (as with Marked by Power) because it will want to stay hidden. Because he didn't willingly do any of this he wouldn't qualify for the Lawbreaker stunt (yet) but if a warden found out about the OI, he would probably convict NA of breaking the 7th. This gives two options: take power from the OI as harry did with lash or stick with just the OI. If NA takes power then, depending on the outsider, you can go in one of two ways. Either this is primarily physical granting things like toughness (anti-magic like an outsider), Speed, Strength, Recovery, etc. or Sponsored Magic. I would simply disallow the latter right here and now because you'd have to create your own Sponsored Magic for outsiders because, no, it wouldn't be the same as hellfire or anything else for that matter. Hell, it might even be unique to this one outsider. Either way, for EVERY power granted by OI it would be a separate violation of the 7th Law and this time earning him the Lawbreaker [7th] stunt each time. I would probably also have the sponsored magic's rule with debt for every time he invoked the physical things, also.
If NA takes power from OI at all then yes, he's a Lawbreaker and the warden in the party will be REQUIRED to behead him or become a warlock himself. If NA doesn't then OI can go by unnoticed and just provide really in-depth flavor to the story until he "comes out" to the party. By this point they will know NA, the good in him and likely hear him out. The Warden will be conflicted but likely side with NA as someone who was just in the wrong place at the wrong time - Not a Lawbreaker. Past that, he will require NA to turn himself in and thus be able to be helped by the council. The Gatekeeper will see the poor soul that is NA when this happens. He can free NA after finding out what happened (thus preventing time paradox!) by banishing the OI back beyond the gate.
The main problem with this is that that's the ONLY way I can see this working other than everyone becoming warlocks. In other words it would be STUPIDLY complex for NO GOOD GOD DAMN REASON! Simply put: Don't allow it. Why? The above.
