Need feedback on possible house rule for concentration check

[Buttmonkey]

I've been fiddling around with a possible SIEGE check for spellcasters who are injured while casting spells to see if their concentration is broken. What I've come up with so far is this:

Excerpt from my house rules wrote:
Spell casters must inform the CK (DM/GM) before initiative is rolled if they intend to cast a spell and what that spell will be. If the spell caster is successfully assaulted (i.e., hit by a weapon, affected by a harmful spell effect, etc.) before casting the spell, the spell caster must make a SIEGE check to determine whether their concentration has been broken. Wizards and Illusionists must make a check against Intelligence and Clerics and Druids must make a check against Wisdom. The Challenge Class will be the Challenge Base (12) + the spell level of the spell being cast by the PC + the amount of damage, if any, taken by the character. The PC gets to add their level to their SIEGE roll as well as their attribute bonus, if any. If the PC passes the SIEGE check, the spell is disrupted, but the PC does not lose the spell (meaning the PC can cast the spell in a later round). If the PC rolls a natural 20 on the SIEGE check, the PCs concentration is not affected at all and the PC will cast their spell that round. If the PC fails the SIEGE check, they lose the spell entirely and must rememorize it before it will be available again.

Example: Buddy is a third level wizard. Before the PCs roll initiative, he declares his intention to cast magic missile, a 1st level spell. Buddy rolls a 1 for initiative and will act last in this combat round. A bugbear hits Buddy with a club and does 3 hit points of damage to Buddy. When Buddys turn comes around, he must make a SIEGE check against Intelligence to determine whether his concentration was broken. His challenge class is 16 (12 base + 1 for the level of the spell (magic missile) + 3 for the hit points he lost in the attack). Buddy rolls a 13, but due to his high intelligence attribute bonus of +2 and adding his level (3) to his roll, he gets a modified 18. This is higher than 16, but not a natural 20, so his spell is disrupted, but he can cast magic missile again next round without having to rememorize the spell.

NOTE: If a spell caster is affected by a magical effect that would prevent the PC from casting the spell altogether (e.g., the PC is paralyzed and the spell has a verbal or somatic component), the PC will automatically lose the spell without a SIEGE check.

I'm concerned with how this will work at high levels. E.g., a 20th level wizard casting a mid-level spell would need to take a butt-load of damage before running a real risk of having her concentration broken.

Anyone's input would be appreciated.

[Fizz]

Actually, this is semi-related to thsoe of us who have tried spellcasting as a Siege check.

Instead of using the spell level in the CL, use twice that. After all, you can't cast a spell of level X until you're level X*2 - 1. It makes sense that the CL increases at twice the rate of spell level.

And it'll definitely keep those checks from being too easily made.

-Fizz

[slimykuotoan]

I'm not sure I'd use spell level in the CL, just because I tend to view the actions used by the caster similar regardless of the spell being cast, with just the caster's knowledge allowing him to do cooler stuff at higher levels, and not his verbal, somatic actions...

If we view the somatic actions getting more complex with spell level, pretty soon we have a wizard standing on his head, rotating sidways, reciting fourty-four sutras, etc. untill it'd get ridiculuosly time consuming.

I'd just use damage taken or something.

[serleran]

Any system you implement is a bonus to the caster because, by the rules, any hit during casting automatically disrupts the spell... so, even giving them a "need to roll a natural 20" is a benefit they would not ordinarily have. After that, you can decide how easily you want them to keep their spells. Sounds to me as if you'd rather them not drop spells too often. To that effect, I would make it a non-SIEGE check akin to SR: start it off at 6 + spell level - attribute modifier. The caster has to roll above this on a d20 to keep the spell.

[Buttmonkey]

Fizz wrote:
Actually, this is semi-related to thsoe of us who have tried spellcasting as a Siege check.

Instead of using the spell level in the CL, use twice that. After all, you can't cast a spell of level X until you're level X*2 - 1. It makes sense that the CL increases at twice the rate of spell level.

And it'll definitely keep those checks from being too easily made.

-Fizz

I think I like this suggestion the best. This is the sort of thing I'll just have to playtest and see what works for my group.

Thanks, everyone, for the feedback!

[Buttmonkey]

serleran wrote:
Any system you implement is a bonus to the caster because, by the rules, any hit during casting automatically disrupts the spell... so, even giving them a "need to roll a natural 20" is a benefit they would not ordinarily have. After that, you can decide how easily you want them to keep their spells. Sounds to me as if you'd rather them not drop spells too often. To that effect, I would make it a non-SIEGE check akin to SR: start it off at 6 + spell level - attribute modifier. The caster has to roll above this on a d20 to keep the spell.

When I first started running C&C, my house rule was that a wounded spellcaster was unable to complete the spell, but didn't lose it and could cast it again the next round. I've decided that is too nice. So, for my players, the natural 20 isn't as much of a bonus.

[Joe]

Keep it by the book.

Those puny spellcasters need to keep the fighting to the warriors.
Back off and stay out of the way is my suggestion.

IMHO 3.5 and the skill concentration makes attacking a spell caster almost a non tactic.

Every spellcaster worth his guff maxes out of concentration which makes for an easy die roll. I have been frustrated more than once by going after the mage, and he just brushes off devastating hits just because he knows how to concentrate.

I prefer the old school way, or the C&C way out of the book.

[Buttmonkey]

Joe wrote:
IMHO 3.5 and the skill concentration makes attacking a spell caster almost a non tactic.

Every spellcaster worth his guff maxes out of concentration which makes for an easy die roll.

What is this "concentration skill" of which you speak?
I never played AD&D after 1E and have no room in my universe for skills, FEATs, or any of the other rules bloat I've heard about from 3E.

Keep in mind that the concentration SIEGE check runs both ways. Enemy spellcasters get the same benefit.

[Jonathan of White Haven]

serleran wrote:
Any system you implement is a bonus to the caster because, by the rules, any hit during casting automatically disrupts the spell... so, even giving them a "need to roll a natural 20" is a benefit they would not ordinarily have. After that, you can decide how easily you want them to keep their spells. Sounds to me as if you'd rather them not drop spells too often. To that effect, I would make it a non-SIEGE check akin to SR: start it off at 6 + spell level - attribute modifier. The caster has to roll above this on a d20 to keep the spell.

This is correct according to page 48 of the PHB, "Concentration". However, that section also says the CK may allow a concentration check vs the appropriate attribute (typically INT or DEX, though I'd allow a WIS check for divine spellcasters) to see if the spell is disrupted (and not lost) or even not interrupted at all.

The way I house rule it is that if the spellcaster takes damage prior to taking his action during the combat round (due to initiative), he must make a successful Concentration check vs. his INT or WIS (arcane or divine) in order to cast his spell. If he fails, the spell is disrupted but is not lost. I also have the option of increasing the challenge level depending on the severity of the damage. For example, being grazed for 1-2 HP remains CL1, while getting hit by a fireball would push the Concentration check up to CL5 (or more, depending on how bad the damage is.)
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"You don't understand, Beaufingle", said Lungwort cryptically. "You ARE dinner." -- M.M. Moamrath

[Fizz]

You know, you could base the CL on the total HD of the attackers, not worry about damage. I mean, even if you don't get hit, it's got be annoying having swords or clubs flying around and at you.

-Fizz