Usurping a Rift

[Plane]

Book of Magic pg 228 under the 13th ability of "powers of stone pyramids" mentions this:

"a 1-53% chance that a being from another dimension may usurp control of the dimensional portal if the portal connects to the beings home dimension"

"Having a Rift usurped means that the character who originally opened the portal has completely lost all control over it.
The alien intelligence who dominates that world controls the portal and can instantly close it, or keep it open"

Mechanically though, what abilities can creatures have that actually do this?

The closest I can think of is that new ability of the Shifter from 2003 in DB7 (RUE reprinted in 2005) under their Dimension Sense where they can "alter the course" or "redirect" which involves matching the PPE cost of an ability and winning a d20 contest.

One of the results of that is "remain open so he too can go through it" which seems to cover this whole "usurp control" aspect.

Are there other spells like this I'm missing? Like if a Vampire Intelligence is not a Shifter I'm not sure how they pull it off exactly.

Pg 33 of Vampire Kingdoms reclassified the AIs from Line Walker to Line RIFTER which might imply they're capable of Teleportational Hitchhiking (RUE pg 117) but it doesn't seem close enough since that's a self-only ability and what AIs do to pyramids is keep a rift open for their MINIONS to go through.

They can all do Dimensional Portal and Re-Open Gateway so Idon't know if one of these might serve the role somehow - like basically if you cast Dimensional Portal on an existing Dimensional Portal, you should be able to use that existing tear to target the dimension it's linked to, in effect forcing the old one to remain open and gaining control of it?

[Warshield73]

I have always read this as more of an ability given to an AI by being in its home dimension not a power of the AI itself. Open a portal to Rifts earth and the VI intelligence cannot do this. Open a portal to its home dimension and it can.

Question is, what is a home dimension?

[Plane]

Another similar instance I recall: RUE 194 had the Becalmed Rift mention under World Links that it can be used as conduit to create witches by powerful supernatural beings - the previous section gave examples of demon lords, gods and AIs. Communication is suggested via empathy or telepathy or magic - you can't step through the rift and it's not clear if sound can travel. Presumably a magic pigeon couldn't go through either...

It also talks about in the next section how the entity will "let go" of the circuit to make it available for other supernaturla powers as soon as it has accomplished cult goals.The distance these things can reach beyond the portal ranges from 1 to 16 miles...

I don't know why (considering how AIs can be competetive) why they would "happily" let go of a Becalmed Rift though.. .unless there was a cost to them of monpolizing it which they will no longer be charged? Like if it cost a PPE per minute (the rift only supplies 1D6 per 5 - not enough to pay that) eventually it would be a drag if the area around the rift was mined for minions and pointless to monitor?

Pg 196 has "Alien Controlled Rift" which costs 100 PPE per minute, for comparison, though that allows actual travel. The ACR seems like a closer match to what AIs can do to pyramids... that might be a fair cost?

I guess the question is - do we just let any AI or god pay that 100 PPE for going ACR ? Where would the line be drawn?