D&D 5E Call Woodland Creatures

[Werebat]

Does the 4th level Call Woodland Creatures spell let the caster choose which creatures are "called", or just the CR of said creatures (letting the DM decide)?

Because summoning eight pixies with a 4th level spell... Sweet Mystara.

 

[ExploderWizard]

In general, the player chooses the CR and thus number of creatures summoned. The DM determines what actually shows up. Pixies in a forest setting make sense. In the underdark, not so much. Think of the environment the druid is in when he/she casts the spell and what would be most likely to appear. For the sake of fairness you can work out some tables based on terrain/environment type and let the player roll what they get.

 

[Illithidbix]

It got covered in a Sage Advice
http://dnd.wizards.com/articles/features/sageadvice_july2015

When you cast a spell like conjure woodland beings, does the spellcaster or the DM choose the creatures that are conjured?

A number of spells in the game let you summon creatures. Conjure animals, conjure celestial, conjure minor elementals, and conjure woodland beings are just a few examples.

Some spells of this sort specify that the spellcaster chooses the creature conjured. For example, find familiar gives the caster a list of animals to choose from.

Other spells of this sort let the spellcaster choose from among several broad options. For example, conjure minor elementals offers four options. Here are the first two:

One elemental of challenge rating 2 or lower
Two elementals of challenge rating 1 or lower
The design intent for options like these is that the spellcaster chooses one of them, and then the DM decides what creatures appear that fit the chosen option. For example, if you pick the second option, the DM chooses the two elementals that have a challenge rating of 1 or lower.

A spellcaster can certainly express a preference for what creatures shows up, but it’s up to the DM to determine if they do. The DM will often choose creatures that are appropriate for the campaign and that will be fun to introduce in a scene.

 

[evilbob]

This is sort of a long-standing debate, and only because of exactly the situation you mentioned: either the spell is (nearly) completely worthless, or it's excessively, (nearly) game-breakingly powerful if you summon the pixies.

The sage advice says that the DM chooses, but on the other hand that puts the DM in a bad spot: either this spell was wasted or it just broke something. In truth, the best situation is that the DM heads this off early: talk to the player who receives the spell and let them know about the situation. Work out ahead of time what's going to happen so the player knows that either this spell should never be prepared or if the pixies will have minds of their own or it's going to be spectacular or whatever works best for your campaign. (For what it's worth, I ran a game with this spell and let them know it would be spectacular and the player understood the situation and used it very sparingly.)