Counterspells

I've been thinking a bit about the idea of counterspells over the years, probably since reading a brief example of it in Weis and Hickman's Deathgate Cycle years back. And none of the iterations I've seen of it quite sit right. In my mind:

• There should be some chance of failure. This is something done on the fly, so it doesn't always work.
• It should have some price. You can't just try it against every spell thrown against you.
• It should not be just one spell or power that everyone needs to take (taking up a slot). It should be a bit more reflective of the breadth of a magician's understanding.

But I hadn't really thought through all the specifics of what that would entail until reading The Robgoblin's post on Beyond Vancian Magic. I still am not fully onboard with his thoughts for this particular talent. But reading it lead me to more thoroughly consider the details of how to write this up for the Ancient Red Wyrm advanced edition.

Other notes:

The text below references mana use. Ancient Red Wyrm uses spending (loss until short rest) or burning (loss until long rest) of mana to cast spells (at least 1 point per spell level).

On additional consideration, it's suggested that counterspells be treated as an optional rule because they add a level of complexity to magical combat, can take some thought to adjudicate, and the negation of actions may be frustrating for players whose magician characters are expending mana to no effect. If players are interested in the idea, then maybe try it out for a couple combats and see how they like it before adopting it as a regular possibility in games.

A “counterspell” is any type of spell which instantly negates the effect of another spell already in the process of being cast. To be used as a counterspell the spell in question must be current prepared by the magician or instantly accessible through other means (e.g. scroll). Several categories of spells work as counterspells:

• Dispel Magic – This spell can be used to counterspell for any type of spell being cast.
• Antipathy – If a spell is in some way the opposite of a spell being cast, then it may be used to negate a spell. For instance inflict wounds may be used to counter a heal spell being cast.
• Sympathy – If a spell is in some way closely similar in nature to a spell being cast, then it may be used as a counterspell. For instance a magic missile may be used to negate another magic missile or a ray of frost may be used to counter a cone of cold.
• Thematically Appropriate – A spell may be used as a counterspell if the caster can make an argument that it thematically functions against the spell being cast. For example a wall of iron conducts electricity and may negate a lightning bolt, or the colors of prismatic spray are a phenomena related to light and could be countered by a darkness spell.
• Mental Effects – Charm and illusion spells which influence or distract the caster or cause them to mis-target can be used as counterspells.
• Defensive In Nature – Any spell that count theoretically counteract or block another can be used as a counterspell. Spells providing mental protection can counterspell those causing psychic damage and those that protect against physical damage can counterspell those causing physical damage.

No matter which category of spell is used as a counterspell, there are a few details which set this use apart from standard use of the spell:

• Awareness of what is Happening – In order to use a counterspell, a magician must be aware that an opponent is creating a magical effect. If the magician can not see or hear that a spell or spell-like effect is being cast, then they can not counterspell against it.
• Instant Casting – Only spells which take a single standard action or less to cast may be used as counterspells. Using the spell as a counterspell happens immediately and uses up the counterspell caster’s action for the round (though they may still move or take free actions when their regular initiative occurs).  
• Spell Level Requirements – Spells of 0-level may only be used to counterspell other spells of 0-level. Any spells of 1^st level or above require another spell of 1^st level or above to negate them. However, the spell used as a counterspell may be of lower spell level than the one being countered (see Chance of Failure below).
• Mana Requirements – If an attempt at counterspelling fails, then the mana used is expended but not burned. Counterspelling only burns mana if it is countering a spell that burns mana.
• Momentary Duration - The spell used as a counterspell ends immediately, even if it would normally have a longer duration. It consumes mana as normal and is completely expended in negating the spell being cast.
• No Other Effect – The act of using a spell as a counterspell means that this specific instance of casting can only negate the spell it is used against. For instance a Fireball used as a counterspell might stop a Wall of Ice from taking effect, but the Fireball would not damage any objects nearby or set anything on fire.
• Chance of Failure – Since they are done quickly, at a moment’s notice, the act of casting a counter-spell is not a sure-thing. In order to succeed, the person making the attempt must make a d20 roll + Casting Ability Modifier (+ Proficiency bonus if proficient in Arcana). The DC is 16 +1 for every point of mana the counterspell caster spends beyond what the original caster did, or -1 for every point of mana the original caster spent more then the counterspell caster did.  Even if the attempt to counterspell fails, the mana used is still expended.
• Limited Countering – Counterspells can only counter spells or spell-like effects. They do not work against other types of supernatural abilities.