No Man's Land
If a cantrip is on you PHB spell list you can cast it. IF you add to your somehow, those are also available.
In addition to by means of the normal counterspell spell, you can attempt counter another's spell casting with a reaction, if (1) you have the same spell prepared (or otherwise available), and (2) you are aware of the spell being cast and able to perceive the target, (3) the target is within range of the spell or within 30ft (whichever us longer), and (4) have a spell slot of sufficient level to cast the spell. To succeed you and the other caster make Concentration Checks (Con saves). Whoever rolls higher wins. In a tie, reroll, until you have a winner. If either fails her own concentration check (dc10), she loses any concentration spell. Either way, you lose the spell slot.
AREA EFFECT SPELLS – COVER
If a creature who is not in the area of effect of a spell (or effect) is in melee combat with another creature who is in the area of effect, it provides 1/2 cover (+2 Save) to Area Effect spells which have Dexterity saves, to the creature(s) it is in melee with. If the saving throw is made because of that bonus, the creature who provided it cover must make a save (with the same +2 cover bonus) or be affected by the spell (or effect). If both creatures are in the area of effect no special rules apply.
If you spend an action concentrating on a concentration spell (assuming no action is needed to use the spell). You get Advantage on your Concentration Roll.
Casters may personalize their spells with minor alterations to the effect. This may grant some small role playing benefit (difficulty to recognize, surprise, bonus to intimidation, etc.) along with a compensating penalty (recognition, limited or delayed effects). Consult the DM with your suggestions. Learned spells (Warlocks, Wizards) require the caster learn each variation, granted spells (clerics, druids) may come “pre-personalized.”
Spells such as Charm Person, Detect Thoughts and others can be cast ‘subtly’. Doing so gives the target Advantage on saving throws, BUT, they don’t know that they’ve been affected by the spell. This does not conceal the magical effect from Detect Magic.
INSPIRED SPELL CASTING
You can use your Inspiration to cast a spell you know but have not prepared, assuming you have a spell slot of sufficient level.
SWAPPING PREPARED SPELLS
Casters that prepare spells may swap up to half (round down) their spell casting class level (paladins 1/4) in spells prepared with a short rest (this precludes any other short rest activities: healing, identifying magic items, etc..) So a 4th level caster can use a short rest to swap one or two prepared 1st or 2nd level spell(s) for another one or two 1st or 2nd level spells. This can’t change the number of spells a caster can have prepared at one time. Once a caster has done this, she cannot do it again until after a long rest.
Alchemists, Apothecaries, Hedgemages and others can offer special components that can enhance the effects of various spells. A character with Alchemist Tool proficieny can learn the recipes to produce such components.
‘BONDED’ MAGIC ITEMS
Some unusual magic items can be bonded to a character. These have level dependent abilities, so they grow as you do.
One use items like potions, a ward is placed either on a shield, armor or piece of clothing. It acts as an innate counterspell (DC10+Spellcaster’s Con Save Modifier) against the specific spell it is warding against. Only one ward can be on a person at a time. It requires a casting of the spell to create the ward.
ALTERNATIVE SAVING THROW
Most saving throws, including those of spells, have an alternative saving throw that can be made at a Disadvantage. So a Fireball requires a Dex save, but could have a Constitution as an alternative save. Such a save would need to be made at Disadvantage. Any save related features (such as evasion, resistance) do not apply when you use an alternative save. What constitutes an alternative is determined by the DM.
Once per long rest a character may attempt to use an alterntive saving throw versus a spell or other effect without disadvantage. For example a Fighter might use Strength to resist a Hold Person. The Player needs to explain how the alternative save makes sense in that case. Doing so uses a Hit Die.
A character can use an action to make a roll of the above skills to detect the presence of magic (skill depending on the source).
- DC20-Spell Level = Active Spells within 30ft
- DC25-Spell Level+hour past = Spells past duration
- If one minute is taken searching give +5 to roll.
- If spell was cast Subtely, make roll at disadvantage.
- If character is in combat, make roll at disadvantage.