Here's an interesting possible non-combat way to use Conjure Woodland Beings.

The only CR 1 fey are Dryads and Quicklings, so if you choose CR 1 you've got a 1 in 2 chance to get Dryads, unless the DM really doesn't want you to have Dryads, or else just lets you choose Dryads. (Personally if I run I'd have the caster make a straight spellcasting ability check to try and get some degree of control over the creature type, since they are expending a valuable spell slot hoping for a certain outcome. The DC to get what they want could be say 15, variable at the DMs discretion. So there's a chance of failure, but a chance of success).

So provided you have the time, summon 2 Dryads. They each cast Goodberry 3 times, that's 60 points of healing divided among whoever you choose for a 4th level spell. That's much better than an out-of-combat 4th level Cure Wounds. And it doesn't put the pressure on the DM with a ton of creatures to keep track of in combat that most of the druid's conjuration spells are guilty of.

Downsides are, your DM might not choose Dryads / not let you choose Dryads / will choose Quicklings just to spite you trying to work the system. And it can't be cast as an action, so it can't be used in the middle of combat like Mass Cure Wounds. Definitely a preparatory or post-combat strategy. Ask your DM beforehand if they like to choose the creatures for conjuration spells or if you can, and that can help you decide if you go for it. Personally I think the DM should give any player who's not trying to throw 8 sprites into a combat encounter a little love when picking the creature.

But if all else fails you still get two new buddies for an hour!

here's another interesting possible non-combat way to use it: take eight pixies out drinking and work with the DM to set up a bunch of quest hooks for the next morning based on severity rolls and the shenanigans you got up to.

I really really am enjoying the idea of eight blink dogs running around in a blink dog park.

Critical Role brought me here...

Episode 49 Season 1

If i use 8th level slot to summon three Sea hags. Do they form coven?

Quote from TattiXD >>

If i use 8th level slot to summon three Sea hags. Do they form coven?

 I love this idea. A bit unbalanced by adding a new set of spell slots to your spellcaster, but i would assume you'd lose those slots if one hag dies. 

I'd strongly consider it as a DM since it *is* a clever use of this spell for an expensive slot use

They need to clarify this spell that it is the GM who selects the actual creatures summoned: https://www.sageadvice.eu/2016/04/09/conjure-woodland-beings-pixies-and-giant-apes/

8 Pixies....8 casts of Polymorph.....for one 4th level slot....

GIVE ME 8 TYRANNOSAURUS REXESES!!!!

Thank you. I have been looking for this.

Quote from DnD_Camel >>

8 Pixies....8 casts of Polymorph.....for one 4th level slot....

GIVE ME 8 TYRANNOSAURUS REXESES!!!!

 Pixie: I have no idea what a Tyrannosaurus Rex is supposed to be. I'll go with a squirrel instead, those are cute! :D

RAW when Hags form a coven their CR value increases, the spell says you have control over a creature of CR 2 or lower. As a DM, if you the player directed for them to form a coven you could argue when their CR rating rises you lose the ability to control them and they attack you. 

Quote from blue_beak >>

RAW when Hags form a coven their CR value increases, the spell says you have control over a creature of CR 2 or lower. As a DM, if you the player directed for them to form a coven you could argue when their CR rating rises you lose the ability to control them and they attack you. 

 Technically you still maintain control of them, as the spell doesn't specify you can only control a creature of CR 2 or lower, only that you can summon creatures of CR 2 or lower, and then proceeds to say "The summoned creatures are friendly to you and your companions." Followed by "They obey any verbal commands that you issue to them (no action required by you). If you don't issue any commands to them, they defend themselves from hostile creatures, but otherwise take no actions." The spell doesn't indicate anywhere that you can only *control* CR 2 or lower creatures, that's just the limit on what you can summon. 

This is a spell that can be quite useful out of combat, and is different from the other Conjure spells in that the summoner creatures are sentient.

The sage advice compendium “clarification” on this and spells like it, is obviously meant to be a “fix” for the pixie issue. This is such a lazy way to fix that issue. This “clarification” causes a whole different set of arguments and disappointment for players. Just errata the MM pixie and take away polymorph. This spell, and even more so conjure animals, is what gives druids like 40% and rangers like 60% of their game balance power. 

if you think of 8 pixies you think of 8 t-rex's or somthin no 4 flying t-rex's

Quote from TattiXD >>

If i use 8th level slot to summon three Sea hags. Do they form coven?

 I think that it only works with specific hags. I;d let it if my player wasn't awware/didn't push it

Would've been more useful if you can control which creatures show up. Some ideas I'd come up with are:

• Killmoulis would be useful for those that used up all their hit dice (raw - you only gain back half your hitdice on a long rest).
• Dryad: A spare 4th level+ spell slot can be used before a long rest to scout a forest and have the dryads charm 1 humanoid for local knowledge or charm/lure 3 beasts to the party so there's no need to hunt for food. Alternatively the Dryads can help to forage for food and scout for fresh water source to help with survival.
• *already mentioned in other comments* Dryad: a feast of goodberries - 30 hp per dryad
• Dryad - those with the painter's supplies tools can attempt to paint the beauty of the Dryads and sell for high price to nobles
• Pixies - out of combat. Attempt to "trade" with the pixies for their pixie dust payment can be sweets or practical joke items - what use does pixie dust have? Those that have access to the "Storm King's Thunder" adventure will see that (for that adventure at least) pixie dust has the following quality: "One pinch of the pixie dust can substitute for the material components of any enchantment spell of 3rd level or lower. The pixie dust has other magical effects as well. If a pinch of pixie dust is sprinkled on a creature, roll percentile dice and consult the Pixie Dust table to determine the effect." Overall a useful commodity that can potentially be traded to NPC merchants

8x Pixies with Polymorph and Fly etc? Yeah nah, there is a reason you can't pick your fey

The spell specifically doesn't say who gets to choose what creatures to summon for this reason which defaults to "the DM makes the rules" - let me know if there's a sage advice on this topic.

Only say nah if players are abusing the spell. I mean come on - medium to high level party engages in an encounter with a CR rating much lower than than their party's level (obviously means that there's other ways to resolve the encounter rather than violence) - why wouldn't you allow 8 T-rexes to go to town if they choose to skip your carefully made content but with a flair?