GameBanshee Forums

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how does IWD2 calculates the spell DC / spell resistance / saves ?



offensive:

- AFAIK: the attribute bonus (WIS, INT or CHA) increases the DC

- but does the caster level count also ?

- spell penetration gives +2/+4 on DC - but also against reflex / fortitude / will saves ?

- does spell focus stack with SP ?



defensive:

- on what depends your basic / natural spell resistance

- how does spell resistance work together with saves (reflex/will)

- does the level of the attacked character counts ?

- and how much is 30 spell resistance given from an item ?


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how does IWD2 calculates the spell DC / spell resistance / saves ?



offensive:

- AFAIK: the attribute bonus (WIS, INT or CHA) increases the DC
*correct*

- but does the caster level count also ?
*yes*

- spell penetration gives +2/+4 on DC - but also against reflex / fortitude / will saves ?
*no, Spell Penetration helps you beat an opponents Spell Resistance, not their saves. Spell Resistance is checked before a saving throw is made. Spell Focus helps you beat your opponents saving throw.*

- does spell focus stack with SP ?
*see above*



defensive:

- on what depends your basic / natural spell resistance
*most creatures/characters do NOT have spell resistance. Items and spells can give it to you, however.*

- how does spell resistance work together with saves (reflex/will)
*No effect*

- does the level of the attacked character counts ?
*The higher your caster level, the harder it is for your opponent to resist. The creature's level that is being attacked doesn't matter unless it is a creature whose Spell Resistance is based on level (like Drow).*

- and how much is 30 spell resistance given from an item ?
*depends on your level and the level of your opponent. If you are level 16 (the level my party finished the game at) then 30 is pretty good spell resistance. Unless it is your opponent that has 30 Spell Resistance (that would make it fairly difficult to use magic against them).*

*a final note: There is always a random element involved (usually a D20).*

.
thanks !


so that I understand it right - just one example:



my level 8 Sorc / level 1 Paladin with 18 CHA, SP and GSF evocation

casts a fireball on a

level 8 drow wizard with 16 DEX




step 1: checking spell resistance


defensive: the drow has 19 spell resistance (11 basic + 8 level)

offensive: my Sorc/Pal gets 8 DC from his 8 Sorc levels and 2 from SP - together 10


calculation: 10DC (+ D20?) against 19 SR + D20 ???




step 2: checking reflex save (only when DC > SR)


defensive: the level 8 wizard has 2 reflex save + 3 bonus from DEX 16 - together 5


offensive: my sorc gets +4 from GSF evocation


calculation: 5 reflex-save against D20 + 4 GSF

> if the dice is 1 the drow makes a succesful save, if 2 or higher he fails ???



GSF seems to be very helpful - but is spell penetration good for anything ?

> against a non-spell resitant enemy it may help a little bit (your caster acts as if he is 4 levels higher but against spell resitant enemies the +4 won't help much!?)


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You cast a spell, and roll level+bonuses (spell penetration, for example)+1d20. if that is higher than the opponent's CR, the spell pierces. It. The DC of the spell is 10+spell level+ability modifier+bonuses(spell focus, for example). The base save of the drow depends on his class, but is always 0.5*level+2 for good saves, level/3 for bad.

So for example, a 12th level barbarian has a base fortitude save id 0.5*12+2 =+8, while his reflex save is 12/3 = +4.

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thanks for your replies - but if I put both answers together it's still a little bit confusing !


could anyone clarify this issue a little bit ???


and btw. ...

...what is the opponents CR ?

....and what determines the basic DC of a spell ?


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CR is Challange Rating. It's a way of measuring 'monster level'.

The basic DC of a spell is determined by the spell's level and the caster's level and a D20.

Originally posted by Sirperry
CR is Challange Rating. It's a way of measuring 'monster level'.

The basic DC of a spell is determined by the spell's level and the caster's level and a D20.

ok, the offensive calculation -step one runs this way:


DC = spell-level + caster level + spell penetration + D20



where do I get the CR - I understand how to calculate this for a drow - but what about the other monsters?


CR = SR + natural SR + D20 ???

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DC and Spell Resistance

Reading over this tread here's what I get so far:

given the Fireball Vs. Drow Wizard example above this is how it would play out-

step 1: check Spell Resistance to see if Drow is affected at all - 'penetration power' Vs. Spell Resistance:

Drow has Spell Resistance (SR) of 19 (base 11 + level 8 charcter) you have a casting level of 8 plus a bonus of 2 from Spell Penetration feat for a total 'penetration power' of 10. You and the Drow both roll a D20 and add this to your total, lets say you roll a 15 and the Drow rolls a 5.

Your total = 8 + 2 + 15 = 25 total
Drow total = 19 + 5 = 24 total

Your total is higher so the spell pierces the Drow's Spell Resistance and he's going to get some pain! How much will depend on his reflex save. Note that without your Spell Penetration feat, the Drow would have resisted and the 'Ball would have no effect at all on him.

Step 2: Reflex Save (only needed if you 'pierce' the Spell Resistance):

Your spells DC Vs. Drow reflex save.

Your Spell's DC= 3 (Spell level for Fireball) + 4 (Charisma bonus) + 4 (GSF Evoc. Feat) + D20 = 11 + D20

Drow reflex save = 1/3 level + Dex. Modifier + D20 = 2 +3 +D20 = 5 + D20

Lets say you roll a 10, your total DC is then 21, the drow would need to roll 16 or more to save and take 1/2 damage, otherwise he's toast.

Mr.Waesel posted that all spells have an additional base DC of 10 which gets added to your total as well (in this case boosting your DC to 21 Plus your D20 giving a min. of 22) but l I don't think this can be correct as it would make your spells VERY hard to save against even without the GSF feat. Even if the Drow in the above situation had to make a will save rather than reflex against a non Evocation spell like Confusion so your GSF doesn't count either and had a Wisdom bonus of +3 (same as his Dex. Bonus for reflex) your total DC would be 10+4+4+D20 = 18 + D20 while the Drow would have a save of 4 (1/2 level) + 3 (wis. mod.) + 2 (fav. save of wiz.) + D20 = 9+D20.

Even if you rolled a 1, he would need to roll at least 10 to save, and if you rolled 11 or higher, he'd need a 20.

In Summary: Spell Focus feats and ability score modifiers like Charisma bonuses for Sorcerors only help make your spell harder to SAVE against and have no impact on whether your spell can 'pierce' a creature's spell resistance. If you do pierce it, you have a better chance that he won't make his save though.

Spell Penetration feats and caster level affect whether you can pierce a spell resistant opponents spell restistance. Against an opponent with no spell resistance, these have no impact (there are however a few spells like Dismissal that use your caster level as well in calculating the DC of your spell, but these are an exception and Spell Penetration feats will not affect this) on whether an opponent will make their save or not, but give you a better chance to get to the point that they have to make a save! Without Spell Penetration or Gr. Sp. Pen., you will have a much harder time against Drow and other spell resistant opponents.

This is my understanding, if any of it is wrong, please feel free to correct it!!!!

I think it is like this:

Spell resistance:
Caster: d20 + caster level + spell penetration
Victim: spell resistance

Saving throws:
Caster: 10 + spell level + ability modifier (CHA, INT or WIS) + spell focus
Victim: saving throw + d20