Anything out there that allows a wizard to maintain concentration on more than one spell, like Greater Invisibility and Polymorph at the same time? Maybe a feat that allows your familiar to maintain concentration for you, minimum caster level 12 maybe? A homebrewed 5th-level Focused Find Familiar?

or to not lose focus with various spells/spell types, like with Focused Concentration for the Conjurer at level 10?

Short answer - no 

there’s a couple legendary/artifact items that don’t require YOUR concentration for a spell (like a sentient magic item can concentrate on a specific spell), but they’re super situational.

i’m sure there’s plenty of homebrew stuff out there though

No. The creators of the game are very clear that there should never be a mechanic that allows concentration on more than one spell at a time. There are cheesy ways to work around that rule, but if you're talking homebrew, you shouldn't be creating rules that directly break that mechanic. And I'm pretty sure there are no wizard options in the rules that allow you to break the concentration mechanic.

Okay. I would have my character use magic items like a Potion of Haste and a Ring of Invisiblity that do not need concentration. 

If that was their intention then they should have thought a bit more when creating the basic rules.

The spell Glyph of Warding allows multiple concentration effects, but it is both expensive and situational to prepare as laying the glyph down takes an hour... however it does allow you to receive the effects of a concentration spell for its full duration without using your concentration. 

What gets around these limitations is the "Spell Gem" item. With this item, you can store the Glyph within it to cast as a single action at a later point. You expend another spell slot when you use the spell gem to "cast the concentration spell" and then the glyph would be set to trigger immediately because you know the circumstances to set (such as "I am standing in the glyph" or "a vampire is in the glyph") the glyph then triggers  and the concentration spell lasts its full duration without using your own concentration.

Spell gem is an item from the "Out of the Abyss" adventure,  but technically the glyph of warding can be used this way since 5e began. Another option is to cast the 8th level spell demiplane (from basic rules) and create a number of glyphs of Warding as your own magical armory. When you need to buff up, just cast demiplane as an action, walk in, say command words to set off the particular glyphs you want, walk out all buffed up with multiple concentration effects that cant be broken and must be dispelled. Admittedly, this does require a lot of money for multiple glyphs, and requires that you are 15th level or higher, but it does work.

Very interesting.

First, Glyph of Warding. The spell does not specifically say that concentration is not needed. For a spell glyph to be useful as a trap, such as by polymorphing a creature into a toadstool, needing concentration would prevent it from being useful. It would end immediately. I believe that is the game mechanic in question. How do you know that is how it works?

Also, you are suggesting I could carry a spell glyph item with me, like an artificer's infused spell in Eberron. Otherwise, I may have to stand in one spot to benefit from it, if concentration would otherwise be required.

(Explosive rune glyph items could also be used as grenades, if I am careful not to drop them. I could hand them out to others in my party. :D)

Casting it within a demiplane sounds the same as within your own home/lair/guardpost/castle, etc. Demiplane 's entrance cannot move with you to my knowledge.

I have Out of the Abyss, so I just now looked up the Spell Gem item. It does not say that concentration is not needed, but it does say that the spell must be on your own spell list. This means it may require what in 4e would be a spell trigger action, used to trigger a spell from a wand or staff. This might be the same game mechanic. You are therefore implying that a spell cast as a spell trigger action, as opposed to, say, from a spell scroll, that concentration may not be necessary.

That does not sound like the intent of the creators of the game. As a power gamer, I do look out for loopholes like that. I would have to confirm it with my DM.

A spell nobody has mentioned yet is also Simulacrum, which creates a duplicate of somebody which retains their abilities (such as spellcasting). They follow your orders and can cast a concentration spell for you. Of course, this comes at the cost of a powdered ruby worth 1,500 gp (or a Wish), and would be probably be painful for a DM so I wouldn't actually advise doing this in a real game without DM permission.

Quote from BoinsterPsi >>

Very interesting.

First, Glyph of Warding. The spell does not specifically say that concentration is not needed. For a spell glyph to be useful as a trap, such as by polymorphing a creature into a toadstool, needing concentration would prevent it from being useful. It would end immediately. I believe that is the game mechanic in question. How do you know that is how it works?

Also, you are suggesting I could carry a spell glyph item with me, like an artificer's infused spell in Eberron. Otherwise, I may have to stand in one spot to benefit from it, if concentration would otherwise be required.

(Explosive rune glyph items could also be used as grenades, if I am careful not to drop them. I could hand them out to others in my party. :D)

Casting it within a demiplane sounds the same as within your own home/lair/guardpost/castle, etc. Demiplane 's entrance cannot move with you to my knowledge.

I have Out of the Abyss, so I just now looked up the Spell Gem item. It does not say that concentration is not needed, but it does say that the spell must be on your own spell list. This means it may require what in 4e would be a spell trigger action, used to trigger a spell from a wand or staff. This might be the same game mechanic. You are therefore implying that a spell cast as a spell trigger action, as opposed to, say, from a spell scroll, that concentration may not be necessary.

That does not sound like the intent of the creators of the game. As a power gamer, I do look out for loopholes like that. I would have to confirm it with my DM.

 

 

 

 From this post, i think you misunderstood what I meant, or perhaps I didnt explain properly. 

1) Glyph of Warding changes a spell that requires concentration to a spell with a set duration.  It specifically states that the spell that is stored lasts for its full duration, which means that even if your dm forces it to use your concentration,  you can immediately drop concentration on it and the spell will persist because of this wording in Glyph of Warding.  This ruling would limit the number of concentration spells you can have to two, but otherwise does not change the situation. EDIT: actually, it wouldn't cap it at two, but it would make it sort of annoying to constantly say you are dropping concentration and then moving on...

2) At no point am I suggesting that you carry a Glyph of Warding with you. Glyph of Warding ends if it moves more than a short distance (iirc 10ft) from the location it was cast. If you cast the spell in a demiplane,  the spell does not move, it is in a set location in that demiplane.  If you store it in a spell gem then it isnt placed until you use your action to cast it *from* the spell gem. In both situations the glyph is not moving.

3) Demiplane is not bound to a location. When you cast demiplane, you create a magical portal to a room in an interdimensional space. The room itself doesnt move, you simply make a new "door" at your location that lasts for a finite duration before closing. You can create a door to your personal demiplane in virtually any and all locations, barring in the presence of a planar ruler that doesnt want a portal to form.

4) The spell gem does not need wording regarding concentration.  We are using the spell gem to get around the long casting time of Glyph of Warding,  not to concentrate on a spell. Any spell stored in a spell gem can be cast as 1 action, even if that spell normally has a much longer casting time. Glyph of Warding says that when you cast it you can expend a spell slot to store a spell in the *Glyph*. So the gem holds the glyph until needed, and then when you use your action to cast Glyph of Warding *from* the gem, you cast the spell that the glyph will hold. The spell gem simply allows you to place and trigger a Glyph of Warding in a single turn.

5) None of what I am suggesting here uses rules from other editions. 4e spell triggers do not factor into this at all.

As a DM myself i probably wouldn't allow any easy ability for additional concentration. Maybe, and just maybe, as a high Level Boon for a Spellcaster. 
I would allow a PC hat uses the Spell Simulacrum, even with a wish spell. Why not? But allow my players to make themselves "invulnerable" and thus to put myself in unnecessary distress? No thanks!

The Reason ist pretty simple. It's stupid powerful and unfun! 

The action- and spelleconomy is what makes encounters challenging and fun. If you allow Spellcasters to concentrate on 2 Spells you will easily find a two Spellcombo that can handle any situation in the game. This discourages teamwork to a great extent and takes away the tension in many situations that your player characters encounter.

Spellcaster are fine as they are. Chase other awesome magical Items or high level spellscrolls, to complete your collection and increase your options for any given situation.

As a fellow dm, I firmly support the thought (and written rule) that every dm has the final call at their table.  It is your prerogative to rule as you like in your sessions. I also agree that multiple concentration spells can trivialize encounters, however I still allow strategies like this... and for one simple reason: the more powerful my players are the more I can throw at them. 

If players repeatedly use such loopholes, i can either balance their rewards to make it more difficult to accomplish OR start sending more and higher CR monsters their way. I personally enjoy large scale fights and being able to use more interesting monsters with higher cr/more powerful abilities in those encounters is one of the scenarios I most enjoy to run. It does make for a more challenging balance, and it can mean that you may overestimate your party, but in my experience, standing against a tide of high level fiends makes for a quite memorable moment.

In which way, do your PC's get multiple concentration Spells? I'm curious.

I've thought about a high level boon (instead of another 9th Level Spellslot for example) or a sentient magic item, like a spellbook or Ioun Stone, with some flaws to it, of course. 
But the more experience as a dm i get, the more careful i am with buffing my PC. Especially if i only buff one PC by a huge margin. 

Quote from RonKubo >>

In which way, do your PC's get multiple concentration Spells? I'm curious.

I've thought about a high level boon (instead of another 9th Level Spellslot for example) or a sentient magic item, like a spellbook or Ioun Stone, with some flaws to it, of course. 
But the more experience as a dm i get, the more careful i am with buffing my PC. Especially if i only buff one PC by a huge margin. 

 read the glyph of warding, spell glyph section - but it doesn't really give you the ability to concentrate on multiple things at once (which is an act, not an effect). its casting an additional spell that then acts on its own even though it normally requires concentration.  That's not really the same thing as being able to concentrate on more than one thing at a time, which a character can never do.

there's ways around a character having to concentrate on something - nothing that allows them to concentrate on more than one thing at once.

Yeah, i know. Other possibilities would be planar binding or simulacrum to get a "similar" effect. But all these ways have reasonable limitations, but if a character succeeds with these tactics it's pure awesome!

I was curious how Barathol_creed grants his PC's the ability to concentrate on 2 spells. With an item, or a boon or anything like that.

Generally, I dont specifically grant the ability I just allow combinations like I outlined above using Glyph of Warding.

I have made a homebrew artifact for a home game previously that allows it. The party in question has limited spellcasting,  so I provided a set of attunement bracers that act as a focus, give a +1/+2/+3 bonus to spell attack rolls (artificts I make follow the critical role stuff where they improve) and would allow the user to concentrate on two spells at the same time, once per long rest. They must make two concentration saves whenever one is required, and if either fail then both spells are lost. 

The easiest way to do it according to the rules is with a Ring of Spell Storing. Give it to a PC who isn’t a spell caster and have the spell casters keep it filled with spells. I’ve also seen a home brewed magic item that did it, but it was in a third party book that I bought so it’s copyrighted. 

Quote from Tim >>

The easiest way to do it according to the rules is with a Ring of Spell Storing. Give it to a PC who isn’t a spell caster and have the spell casters keep it filled with spells. I’ve also seen a home brewed magic item that did it, but it was in a third party book that I bought so it’s copyrighted. 

for the ring of spell storing, you have to use concentration if the spell requires it. It specifically says "While wearing this ring, you can cast any spell stored in it. The spell uses the slot level, spell save DC, spell attack bonus, and spellcasting ability of the original caster, but is otherwise treated as if you cast the spell. "  There is no mention that a spell wouldn't require concentration so saying that is adding to the description.

the glyph of warding is very different, it specifically mentions concentration. (although imo is still open to interpretation, but there's a sage advice out there that discusses it)

What character level?

Quote from HeathSmith >>

Quote from Tim >>

The easiest way to do it according to the rules is with a Ring of Spell Storing. Give it to a PC who isn’t a spell caster and have the spell casters keep it filled with spells. I’ve also seen a home brewed magic item that did it, but it was in a third party book that I bought so it’s copyrighted. 

for the ring of spell storing, you have to use concentration if the spell requires it. It specifically says "While wearing this ring, you can cast any spell stored in it. The spell uses the slot level, spell save DC, spell attack bonus, and spellcasting ability of the original caster, but is otherwise treated as if you cast the spell. "  There is no mention that a spell wouldn't require concentration so saying that is adding to the description.

You are correct, I wasn’t very clear. If the party obtains a Ring of Spell Storing and a non spell caster wears it, spell casters in the party can cast spells into the ring and then the non spell caster can cast and concentrate on the spell.

It doesn’t allow one PC to concentrate on two spells, but it can achieve the same end result by having another PC concentrate on the second spell. 

No problem. Your simulacrum allows to have two concentrations. And touch spells like protect from evil and good may be used through your familiar. In that case your familiar hold concentration on such spells. So that 4 concentration maximum (about familiar read spell find familiar)

What you are describing is a huge powerboost.

I tried it as a feat (https://www.dndbeyond.com/feats/19307-multi-tasking-spellcaster) but thought it too powerful. 

So I redid it as an entire homebrew subclass (https://www.dndbeyond.com/subclasses/160516-focused-mind)