pg 86 discusses how Dream Makers can by "channeling ISP into the membrane" (temporarily, that cost is way too crazy to be permanent!) reduce the chance "of the storm breaking in" where a failed percentile results in a storm "piercing the membrane".
The preceding paragraph talks about how the structures in the path take the same effects previously (being directly in a Dream Storm) which sounds like a pierced membrane means occupants get sucked out of the domain and into the storm itself (like how pg 106 describes the creation of Living Nightmares).
pg 94 talks about how PERMANENTLY sacrificing ISP makes the domain "nearly impossible to breach".
These seem like very similar ideas, so I was wondering how we might adapt the existing canon:
- 1a) temporary ISP spent to protect from Dream Storms
2b) permanent ISP spent to protect from creatures/psychics
Into house rules:
- 3c) temporary ISP spent to protect from creatures/psychics
4d) permanent ISP spent to protect from Dream Storms
The basis of comparison I would use to construct this can also be found on page 94:
- *opening a temporary rift between the real world and the dream world costs 60 temporary ISP for 2min/level
*opening a permanent rift between the real world and the dream world costs 15 permanent ISP
The ratio between these is conveniently 1:4 which makes for simple parallels when adapting to membrane-strengthening instead of membrane-rifting.
So the parallel based on this ratio, when constructing house rules would be:
5 permanently sacrificed ISP is equal to 20 temporarily spent ISP (forever)
20 temporarily spent ISP is equal to 5 permanent sacrificed ISP (for 2 minutes per level)
So basically if you permanently sacrifice 5 ISP, it should count as -2% chance of Dream Storm puncture (reducing 50% chance to 48% chance) indefinitely.
Whereas, if you wanted to temporarily keep out dream travelers, you could pay 20 ISP to get a +15 bonus for 2minutes/level if you wanted to avoid making a permanent expenditure.
The "Create Dream Domain" could probably be broken down into smaller increments too. IE instead of needing to pay a full 5 ISP to get +15 to save, you could pay in permanent 1 ISP loss incremenets to get a gradually ascending +3 bonus per payment.
In the same way, temporary bonuses could also be incremental. Instead of paying 20 for +15, you could pay in increments of 4 ISP to get increments of +3 bonuses.
That might even be broken down into smaller amounts (4/3 cost per +1) which you could round up if the GM doesn't want to track ISP in fractional amounts
[*]2 buys +1
3 buys +2
4 buys +3