works great with a conjuration wizard 

Confused about this spell.....

Is it a way to make say a water elemental do my bidding for up to  year and a day, WITHOUT concentration?  Who the hell could maintain concentration that long?  What if you sleep, wouldn't sleeping break concentration?

Or even with those extreme durations, do you STILL require concentration, and thus there's literally not a chance I'd not accidentally break this by casting hex, or hold monster or something.....

 "Typically, the creature is first summoned into the center of an inverted magic circle in order to keep it trapped while this spell is cast.)  If the creature was summoned or created by another spell, that spell's duration is extended to match the duration of this spell."

What way are people taking this?  Wouldn't this spell be utterly pointless used on anything I summon, if I do have to maintain concentration?

Quote from belfastbiker >>

Confused about this spell.....

Is it a way to make say a water elemental do my bidding for up to  year and a day, WITHOUT concentration?  Who the hell could maintain concentration that long?  What if you sleep, wouldn't sleeping break concentration?

Or even with those extreme durations, do you STILL require concentration, and thus there's literally not a chance I'd not accidentally break this by casting hex, or hold monster or something.....

 "Typically, the creature is first summoned into the center of an inverted magic circle in order to keep it trapped while this spell is cast.)  If the creature was summoned or created by another spell, that spell's duration is extended to match the duration of this spell."

What way are people taking this?  Wouldn't this spell be utterly pointless used on anything I summon, if I do have to maintain concentration?

 For a lot of summoning spells concentration only makes the creature listen to you. This spell overrides that requirement by forcing them to regardless of concentration. A high level wizard can summon the beefiest fiend they want and then, while it is bound in a circle, cast this very long and expensive spell to free up concentration again. It's a neat spell but I think DM's are more likely to get to use it than players. Example; A lich has forced a Horned Devil into its service by using a talisman with its true name and planar binding. For one year and one day it must serve its undead master.

Why is this spell NOT a ritual? Casting time is an entire hour.

Quote from sgtstumpy >>

Why is this spell NOT a ritual? Casting time is an entire hour.

 Rituals can be cast without expending a spell slot. This would be incredibly easy to spam for high level conjurers (and rich) if that was the case. A 20th lvl wizard could summon 8 elementals from cr 5 through 9 with Conjure Elemental and bind them for 30 days. And that's just solo. This is already a super powerful spell since the cost doesn't scale for how long you bind the creature for.

Why would you use this instead of "Geas"?

It extends the length of summoning spells. "If the creature was summoned or created by another spell, that spell's duration is extended to match the duration of this spell."
Geas on top of Planar Binding might be an effective way around the creature twisting your words though. "The creature obeys the letter of your instructions, but if the creature is hostile to you, it strives to twist your words to achieve its own objectives."

How to capture and bind an empyrean

Step one: find the name of one using legend lore

Step two: cast gate and speak it name so they are summoned inside a circle.

Step three: get a cleric to cast bane and a wzard to cast feeblemind.

Congrats you now have a child of god to do your bidding.

first of all, by the time one hour and ten minutes have gone by, the spell has already ended, and also casting this spell EVER requires a lot of preperation so if you did not bring any 5th level spell slots then that is YOUR problem, not the dnd writers

wizards do not get bane, bards and clerics do.

and if you really wanna weaken them, cast feeblemind to make their charisma score an pitiful 1, making catching them easy

also you cannot benefit from several castings of the same spell, please read chapter 10 of the players handbook you lil dork

lastly, yeah this is an great plan. Until you word something far to vaguely and end up ordering your own death

Ok that makes sense with the stacking, I'm kinda new to all of the spell rules.thanks for the feeble mind suggestion  

you're wellcome

note also that bards have bane, ledgend lore and feebleind on their spell list, and they have an feature called magical secrets that lets them learn spells not on their spell list at certain levels, an level 18 bard can theoretically do all of this alone. Also the glyph of warding spell can help you greatly, as it allows you to more or less "store" spells within an symbol that will be cast on an target once a trigger is met, working sort of like an magical trap, it alows you to get arround the limit on concentration.

furthermore, many spellcasters use the magic circle and planar binding spells to make shure the summoned creature does as you say. I assume that that is what you allready meant but you forgot to mention those two spells.

furtherore to make your sucess a little more likely, consider making  your plan a little more elaborate by adding spells like bestow curse or hallow to your setup to try and give the target disadvantage on saves or prevent the empyrean from just using an plane shift spell to teleport away, you have an cleric, does it not feel like a waste to just have it cast bane and then sit there for awhile.

there, that is every improvement to your plan i can think of

Quote from Krodothlhren >>

Why would you use this instead of "Geas"?

 
1) Powerful creatures will happily take the average 28 damage from disobeying a Geas to gut everyone your wizard knows.

2) Geas doesn't work against creatures that are immune to being charmed, and a simple Remove Curse cancels it

3) You can't revise Geas with new instructions for a changing situation -- Geas is much better at giving a creature something to do FAR AWAY from you right now.

Planar Binding requires more investment and is much more powerful than Geas for a more limited and powerful set of targets.

Quote from DIemortalscum >>

How to capture and bind an empyrean

Step one: find the name of one using legend lore

Step two: cast gate and speak it name so they are summoned inside a circle.

Step three: get a cleric to cast bane and a wzard to cast feeblemind.

Congrats you now have a child of god to do your bidding.

 
This might be a recipe for your wizard's worst day, ever.

Feeblemind: "The creature can't cast spells, activate magic items, understand language, or communicate in any intelligible way."

How's it going to "do your bidding" if it can't understand you? It still recognizes its friends, and you're definitely not one of those. A feebleminded creature can't even understand the instructions you give it with Planar Binding.

Love it when ol' wizzy outthinks himself.

This spell is a good way to bring a level 20 druid to heel if they're an elemental-hopper.

Would it be possible to use this spell with the Summon Celestial Spirit spell (assuming two level 5 spell slots available)? 

This looks like a great use for wish.

Feels like it should last until undone by remove curse 5th level+ or dispel good and evil. Far more bad ass and manageable if players want to use it.

Yep! Go up against a big bad of the eligible types. Once you've burnt through any legendary resistances it might have had, wish 8th level casting of this, use portent to guarantee failure of the save (if diviner), and then it is bound for 180 days. Not terrible!