dispel chance

WraithLord · #1 July 7th, 2005, 06:57 AM

I read some older posts regarding dispel.

I wasn't sure about something so I'm bringing it up again.

I will use an example as reference.
Say someone cast a GE that costs 70 gems and added 30 more for strength.
So...

what is the chance of failure if a dispel is cast with no extra gems?- is it 100%?

what is the chance of failure if a dispel is cast with less then 30 gems?- is it 100%?

what is the chance of failure if a dispel is cast with exactly 30 extra gems?

what is the chance of failure if a dispel is cast with more then 30 extra gems?- Is it a guaranteed success (0% failure) or a function of the added gems?

TIA all experts.

Jurri · #2 July 7th, 2005, 08:44 AM

I think there's an open ended roll involved, so there are no guarantees, no matter what you pay

Truper · #3 July 7th, 2005, 09:03 AM

If the dispeller's extra gems spent + skill in Astral magic (or perhaps skill above that required to cast dispel) + oeD6 is greater than the globals extra gems spent + oeD6, the global will be dispelled. So:

Very high chance of failure.

Less chance, but the odds are not good. (depending on how many less than 30 were spent)

Basically 50-50, with a slight edge for a powerful Astral caster.

Arbitrarily low, depending on how many extra gems were spent.

WraithLord · #4 July 7th, 2005, 10:19 AM

quote]Truper said:
If the dispeller's extra gems spent + skill in Astral magic (or perhaps skill above that required to cast dispel) + oeD6 is greater than the globals extra gems spent + oeD6, the global will be dispelled. So:

Very high chance of failure.

Less chance, but the odds are not good. (depending on how many less than 30 were spent)

Basically 50-50, with a slight edge for a powerful Astral caster.

Arbitrarily low, depending on how many extra gems were spent.

[/quote]

This raises an interesting probability question.
What is best cost effective strategy for dispell.
Two extremes, on the one hand trying to dispel with no extra gems. If attempt fails try again.
On the other hand cast dispel with a Hugh amount of extra gems say (relating to the example) 60 gems.
so gem wise three dispel attempts cost the same as one with 60 extra gems.

Another factor to take into account is that actually the amount of extra gems spent to cast to GE is usually unknown.
It could be anything from 0 to whatever.

I want to plot a graph of the chance of dispel dependent on the factor of extra gems.
A basis for this graph is probability of one oed6 to be greater then another independent one.
Say Xa = result of oed6, Xb = result of oed6, P(Xa>Xb)?
For regular d6 I think it something like 15/36.
For oed6 I am not sure. I think is something along the line of:
15/36 (sum of events of Xb less then Xa in first roll) +
1/36*(15/36 + 1/36*(15/36 + 1/36* ...
(event of first roll ties on 6 and then second roll)

I could be entirely wrong so if you are a math expert and reading this I'd appreciate any comments to my reasoning.

WraithLord · #5 July 7th, 2005, 12:19 PM

To get an idea of the probability of successful dispel as a factor how many extra gems the dispelling mage is using I simulated things for d6.

The attached graph is for d6.
I think that the graph for oed6 would be similar except that it is asymptotic to 1.
Therefore I think that if the caster will add 3-4 gems extra to what the GE caster used he would have a good chance for dispelling (~80%-90%).
more then that would give diminishing addition to the chance of dispel.

Well probably that's an obvious conclusion, but I find it useful nonetheless

FrankTrollman · #6 July 7th, 2005, 03:18 PM

I have never seen a dispel cast with more TOTAL gams than the original spell fail. I have never seen a dispel cst with less TOTAL gems than the original spell succeed.

This leads me to believe that there is no open ended die roll involved, and that the bigger spell simply wins. Every time.

Note, the spell doesn't seem to care about how many extra gems are spent, only how many total gems are spent. So a Burden of Time with zero extra gems would need 41+ extra gems to dispel (because a base Burden of Time has 70 gems in it, and the base Dispel has only 30 astral Pearls in it).

Note2, it looks like it's the total gems you actually spent, so if you have been casting spells out of a magic bonus site, it's that much cheaper to dispel them as well.

Note3, this is probably why the minimum Dispel is 30 pearls, as that is coincidentally the minimum cost of any Global Enchantment (Stellar Brilliance, as it happens).

-Frank