PC creating a custom divination spell

[Magic Myrmidon]

Got a PC who found a spell book with literally every wizard spell in it. So he'll be making a new spell or two to leave his mark on the setting.

There were a few ideas tossed around, but the most promising was a concentration divination spell that would identify spells being cast in his presence without needing to use a reaction. He's a fan of counterspell.

What level do you guys think this would be? My gut reaction is level 2, but I wanted some other opinions.

[Unoriginal]

Got a PC who found a spell book with literally every wizard spell in it. So he'll be making a new spell or two to leave his mark on the setting.

There were a few ideas tossed around, but the most promising was a concentration divination spell that would identify spells being cast in his presence without needing to use a reaction. He's a fan of counterspell.

What level do you guys think this would be? My gut reaction is level 2, but I wanted some other opinions.

How long would the duration be?

[heavyfuel]

If you're going to make it a Concentration spell, you may want to buff it a bit. Being able to know what spell is being cast isn't super useful when you compare to other Concentration effects.

I'd say either make it a Bonus Action, one hour duration with Concentration and you automatically know the spell. Or make it a full Action that lasts for only a minute, but no Concentration attached, and only gives you Advantage on Arcana checks to identify the spell being cast.

Both versions have enough drawbacks that someone can't use it constantly. First version's drawback is obviously Concentration, and second version's is that you have to use an Action (so you lose some offensive power), it's difficult to pre-cast because it only lasts one minute, and even with Advantage you're far from guaranteed to make the DC 15+Level chack.

[MoiMagnus]

Lv2 Ritual, concentration up to 10min (or 1h?) seems fine to me, even weak.
You're using your concentration for no direct bonus (most of the time, you would have been able to guess correctly whether or not counterspell is a good idea or not without needing this spell).

I would argue a more balanced version would be an "Improved Detect Magic", so it has all the effects of Detect Magic, plus this new spell identification effect (and maybe extended duration to 1h?) in exchange of being a level 2 (which is not that much of a cost for a ritual, but might still be relevant sometimes).

If that's not a Ritual ... I'd say Lv1 at most. In fact, I think cantrip would be better. Concentration is a huge opportunity cost. If you remove concentration, I'm not sure any more, Lv2 could be fine if it lasts long enough (8h or so, like Mage Armor).

[Magic Myrmidon]

You know, you all have a good point. I was JUST talking with the group about the way the designers overused concentration. It should probably be concentrationless. I'm ok with ritual too.

I like the improved detect magic idea. I'm leaving the decision on actual spell performance to the player, in terms of whether it'll be a variant in an existing spell.

[Meichrob7]

If you’re making essentially a “Greater Detect Magic” then I’d make a concentration ritual for an hour, or make it a non-ritual spell for no concentration that lasts 1 hour.

I’d imagine it being 4th level, that’s where greater invisibility sits so it feels kinda fitting, and bumping it any higher would in my mind make the non-concentration option become less viable since it’s eating up a 5th level slot which is very valuable.

As it is a 4th level slot for something which may or may not be useful and has a sort of niche use as is, is a pretty expensive spell. That’s why I don’t think you should dump it’s duration if it’s not concentration like some people are suggesting.

Another option is to add some interesting spell components. Like maybe it’s 8hr no concentration but it consumes some sort of spell component like a 200gp pearl.

You could also limit in ways besides duration. Maybe it can only identify a few spells or spells at the level it’s cast. Personally that last limitation feels a bit harsh and if you were gonna do something like that I’d be tempted to instead make it like “The spell can identify spells two levels higher than the spell level it was cast at, or anything below that threshold.”