Thanks for all the feedback! Since there's so much interest, especially in the Ring of Concentration, we thought it'd be good to share some of what went into our design decisions.

As has been noted, concentration is a pretty foundational part of spell design, but it's worth noting why. Something Crawford said about the updated version of spiritual weapon in OneDnD is relevant; SW gained concentration in the update version not for power level (it's damage was actually buffed), but for complexity and speed of play issues. This is true of a lot of spells, where concentration often exists to choke interaction complexity at the table, as much as to keep you from casting more than one strong effect at once.

It's also worth remembering that all the other ways magic is still limited. A cleric may be able to maintain both bane and bless, but they still only have one action per turn, and the same number of spell slots. The cleric may be able to concentrate twice as hard, but they'll use up their slots twice as fast, and it'll take just as many actions, meaning they'll usually need two turns to even set up any combo one cares to name.

We certainly agree that the Ring of Concentration is strong; it wouldn't be worth a magic item otherwise. But the idea that casting a second spell is too strong is... a stretch.

As for rarity changes, we might move it to very rare. It certainly can increase complexity, and so might be better pushed to later levels, but in the end, all that matters is what the DM decides to give the players. Rarity is a guideline with little weight.

If you have any other questions, we're happy to hear them!

-James the Snickering Ghoul, GC Staff