The Doctor isn't quite ready to hang his hat on the idea of the rift making such informed decisions, and he's certainly not especially convinced that it operates on a logical and benevolent wavelength rather than a capricious and malevolent one. But the rift might well defend itself and its dream-bubbles if they come under attack, and Callie's brother sounds like he generates a lot of collateral damage to cosmic phenomena. And Iman is definitely right about a couple of things. One, that he's pretty much guaranteed not to let a huge cosmic asshole just casually ruin the universe in which he currently resides. And two, that Callie in particular is a really bad choice of targets. Her aliveness is just too huge and symbolic (and absolving) a triumph. "Oh yes, the TARDIS is the safest place there is. Completely unassailable. And that's not idle speculation, I get assailed all the time. Tends to backfire on the assailants." Granted, that might be less true in a universe where the TARDIS is grounded and on a power ration. And there have certainly been some serious threats. And he knows nothing about this particular potential threat whatsoever. But he'd still give the TARDIS better odds than anything else, in defensive terms. Which is to say nothing of himself.

"Not to mention, being alive might give you some breathing room." Oh, he's hilarious. "He won't be expecting that." Said the Doctor, having not read Homestuck. If he's hunting for a ghost, then the focus will probably be on dream-bubbles. So that's perhaps a concern, but there's time enough to burn that bridge. "And he certainly wouldn't be expecting me."