yes that's how concentration works 

Quote from nmarple >>

Quote from StarrLorde29 >>

If I drop concentration on the elemental, does the DM now gain control of the elemental? Or would you roll a dX to see who it attacks as you have no control?

 i think the elemental spirt is released  and the elemental turns to the element its made of

 The spell actually has a clause about this. "If your concentration is broken, the elemental doesn't disappear. Instead, you lose control of the elemental, it becomes hostile toward you and your companions, and it might attack. An uncontrolled elemental can't be dismissed by you, and it disappears 1 hour after you summoned it." the elemental sticks around if concentration is broken. I would argue that it falls under DM control at this point, just to simplify the process.

Many 1 action and 1 bonus action spells can be "held" for the right opportunity. With this being a 1 minute casting time, can I still prep the spell and "hold" onto it until the perfect moment I would like to finish casting it? I understand that "holding" spells count as concentration on a spell for the means of waiting for a perfect moment. Just didn't know if longer castings meant that could be held.

If it can be held, is it possible to stop the spell if it isn't finished by cancelling the hold and still keeping the 5th level spell slot?

Now I can have a Chwinga as my familiar... this is truly powerful.

So contrary to popular belief, there's no such thing as "holding one's action" in 5e. Instead, characters can take the Ready action. This action, which you can take on your turn, allows you to perform an action as a reaction later in the same round, by choosing a particular trigger on your turn. Since the casting time of this spell is longer than an action, you can't use the Ready action to cast it as a reaction.

That said, according to the "Casting Time" section of the player's handbook, "When you cast a spell with a casting time longer than a single action or reaction, you must spend your action each turn casting the spell, and you must maintain your concentration while you do so. If your concentration is broken, the spell fails, but you don't expend a spell slot. If you want to try casting the spell again, you must start over." This means that you could, in theory, start casting the spell, and if you aren't ready to cast it by the time it would otherwise be cast, you can simply end your concentration without losing the spell slot and begin casting it again.

And as always, a DM is fully within their rights to adjust this however they see fit! It certainly wouldn't break the game if a DM allowed someone to simply continue using their action to prepare the spell, only casting it when the time is right, either as an action or reaction. Hope this helps!

Alas, there is no option to summon multiple elementals of lower CR.... thought generally I don't like summoning lots of things because it can slow down the game

Would any of you DMs out there be picky enough to say that sand doesn't count as earth for the 10 cubic foot requirement of this spell ?

Could a elemental choose to stick around and steak havoc?

It sounds like you can't choose an area smaller than a 10 ft. cube, which means to me that the chosen element must cover at least half of the area to have an effect. It gives an example of a CR 5 Fire Elemental walking out of a bonfire (which are generally large-sized fires, the same size as the elemental).

Would you consider allowing a player to toss a regular torch on the ground and summoning a CR 1/4 fire elemental, or would his only option be an air or ground elemental since the torch is too small?

Beastt

counter spell can be more clutch for fighting bosses with spells, this will likley see more play, though DO NOT LOSE CONCENTRATION, highly recommend warcaster or something similar

Quote from nmarple >>

Quote from StarrLorde29 >>

If I drop concentration on the elemental, does the DM now gain control of the elemental? Or would you roll a dX to see who it attacks as you have no control?

 i think the elemental spirt is released  and the elemental turns to the element its made of

 read the spell, "If your concentration is broken, the elemental doesn't disappear. Instead, you lose control of the elemental, it becomes hostile toward you and your companions, and it might attack. An uncontrolled elemental can't be dismissed by you, and it disappears 1 hour after you summoned it."

Summoning an Invisible Stalker to mess with people can be a lot of fun as a player, but more so as a DM. If you want paranoia to become a part of the game, have a summoner who uses them. 

On the subject of Invisible Stalkers, what happens if you lose concentration while one is summoned? According to the spell description it becomes hostile and MAY attack you. However, according to the information we have on the Stalker, it exists for the sole purpose of obeying its summoners commands albeit begrudgingly "Forced to serve until the magic that binds it expires". Could you theoretically just drop concentration and order it around normally?

Quote from ChaosFighterX >>

On the subject of Invisible Stalkers, what happens if you lose concentration while one is summoned? According to the spell description it becomes hostile and MAY attack you. However, according to the information we have on the Stalker, it exists for the sole purpose of obeying its summoners commands albeit begrudgingly "Forced to serve until the magic that binds it expires". Could you theoretically just drop concentration and order it around normally?

I would argue the magic that binds it expired when concentration ended the spell. 

This is weirdly one of the most balanced spells I can think of. I mean, you can cast anything of CR 5 or lower, at level 9, and once you reach the end of the campaign you can cast absolute boss level things, but if you do, there's the constant threat of possibly having to fight it. Definitely a good spell. And also Xorn is terrifying.

Quote from nmarple >>

Quote from StarrLorde29 >>

If I drop concentration on the elemental, does the DM now gain control of the elemental? Or would you roll a dX to see who it attacks as you have no control?

 i think the elemental spirt is released  and the elemental turns to the element its made of

 it specifically says: "If your concentration is broken, the elemental doesn't disappear. Instead, you lose control of the elemental, it becomes hostile toward you and your companions, and it might attack."

Quote from ThirdMarshall >>

Many 1 action and 1 bonus action spells can be "held" for the right opportunity. With this being a 1 minute casting time, can I still prep the spell and "hold" onto it until the perfect moment I would like to finish casting it? I understand that "holding" spells count as concentration on a spell for the means of waiting for a perfect moment. Just didn't know if longer castings meant that could be held.

If it can be held, is it possible to stop the spell if it isn't finished by cancelling the hold and still keeping the 5th level spell slot?

 the "holding" your action is called readying an action and it has to be 1 action or your movement

Quote from ChaosFighterX >>

On the subject of Invisible Stalkers, what happens if you lose concentration while one is summoned? According to the spell description it becomes hostile and MAY attack you. However, according to the information we have on the Stalker, it exists for the sole purpose of obeying its summoners commands albeit begrudgingly "Forced to serve until the magic that binds it expires". Could you theoretically just drop concentration and order it around normally?

 technically yes, it would continue following your commands i think, it would disappear after an hour, but if you do that at the end of the hour the spell lasts, you can technically control it for 2 hours instead of one

Quote from SylvieTG >>

Quote from ChaosFighterX >>

On the subject of Invisible Stalkers, what happens if you lose concentration while one is summoned? According to the spell description it becomes hostile and MAY attack you. However, according to the information we have on the Stalker, it exists for the sole purpose of obeying its summoners commands albeit begrudgingly "Forced to serve until the magic that binds it expires". Could you theoretically just drop concentration and order it around normally?

I would argue the magic that binds it expired when concentration ended the spell. 

Quote from SylvieTG >>

Quote from ChaosFighterX >>

On the subject of Invisible Stalkers, what happens if you lose concentration while one is summoned? According to the spell description it becomes hostile and MAY attack you. However, according to the information we have on the Stalker, it exists for the sole purpose of obeying its summoners commands albeit begrudgingly "Forced to serve until the magic that binds it expires". Could you theoretically just drop concentration and order it around normally?

I would argue the magic that binds it expired when concentration ended the spell. 

 but the elemental is still bound to the material plane for an hour after you lose concentration