Anti-Magic Redux

It is a common fantasy trope to see epic wizard duels where spells are cast back and forth, being deflected and countered, until finally one side gets the upper hand. It can be hard to replicate that feeling in D&D, with anti magic being relatively high level, and spell-slot intensive. With that in mind, the following options are proposed to promote that fantasy of interactive magic.

Rules Changes

The following rules changes are proposed, with existing rules included here with strikethrough for removals and italics for additions:

Concentration

Some spells require you to maintain concentration in order to keep their magic active. If you lose concentration, such a spell ends.

If a spell must be maintained with concentration, that fact appears in its Duration entry, and the spell specifies how long you can concentrate on it. You can end concentration at any time (no action required).

Normal activity, such as moving and attacking, doesn't interfere with concentration. Whenever you make a Constitution saving throw to maintain concentration, the DC is 10 + twice the number of spells on which you are maintaining concentration, unless stated otherwise.

The following factors can break concentration:

Casting another spell that requires concentration. You lose concentration on a spell if you cast another spell that requires concentration. You can't concentrate on two spells at once.

Taking damage. Whenever you take damage while you are concentrating on a spell, you must make a Constitution saving throw to maintain your concentration. The DC is calculated as above, or half the damage you take, whichever number is higher. If you take damage from multiple sources, such as an arrow and a dragon's breath, you make a separate saving throw for each source of damage.

Being incapacitated or killed. You lose concentration on a spell if you are incapacitated or if you die.

The DM might also decide that certain environmental phenomena, such as a wave crashing over you while you're on a storm-tossed ship, require you to succeed on a DC 10 Constitution saving throw to maintain concentration on a spell.

For instance, if you are maintaining concentration on Detect Magic and Detect Thoughts, any effect which would require a Constitution saving throw to maintain concentration would be at a DC of 14, unless stated otherwise by the effect causing the saving throw.

Arcana

Your Intelligence (Arcana) check measures your ability to recall lore about spells, magic items, eldritch symbols, magical traditions, the planes of existence, and the inhabitants of those planes.

You can also use Arcana to detect and identify magical effects. The DC to detect a magical effect is based on the creator of the spell effect, if applicable. The suggested DC is 10 + spellcasting ability modifier + proficiency bonus for the spellcaster. The DM may increase this DC if the spell effect is not easily detectible, like Invisibility or other illusion magic. The DM may decrease this DC if the spell effect is particularly obvious, like Dancing Lights, or if it is a spell you already know. The DC to identify a magical effect is 10 + twice the spell slot level. You have disadvantage on this check if the spell slot is higher than any spell slot you are currently capable of using. The DM may decrease this DC if the spell effect is particularly obvious, like Dancing Lights, or if it is a spell you already know.

New Spells

Three new cantrips are detailed here, essentially lower-powered versions of Counterspell, Dispel Magic, and Antimagic Field.

These cantrips are on the Bard, Sorcerer, Warlock, and Wizard spell lists. They may also be taken by Clerics with the Arcana domain.

Interrupt Spell

Abjuration Cantrip

Casting Time: 1 reaction, which you take when you see a creature within 60 feet of you casting a spell

1 reaction, which you take when you see a creature within 60 feet of you casting a spell Range: 60 Feet

60 Feet Components: S

S Duration: Instantaneous

You attempt to interrupt a creature in the process of casting a spell. The creature must make a Constitution saving throw, as if maintaining concentration on this spell, in addition to any other spells it is currently concentrating on. The DC to maintain concentration becomes equal to your spell save DC, if it is higher than the normal calculation. The creature gets a bonus to this save equal to the level of the spell it is casting. On a failed save, its spell fails and has no effect, and the spell slot (if any) is not expended.