The Wizard power Foe to Frog (Heroes of the Fey Wild) allows the wizard to change the target into a tiny beast.
My question is: can the polymorphed target retain its spell casting ability if it has the appropriate limbs for somatic movements and a mouth for vocal ability?
An example: a necromancer turned into a frog. Ribbit ribbit (magic missile!). Interestingly enough, I don't consider a frog a beast, yet that is the example given.
I assume that you are referring to Slimy Transmutation (level 1 wizard daily from the red box)
It's effect line reads:
As a toad, the target is dazed and the only actions it can take are to move its speed or shift.
As per the effect line of the power, a spell caster would not be able to cast most, if not all, their spells.
In general, the only limitation on a polymorphed creature taking actions is the explicit effects described by the polymorphing power. Wild Shape (druid class feature) is a good example here. It is a polymorph power, that has the following limitation on actions:
While you are in beast form, you can’t use weapon or implement attack powers that lack the beast form keyword, although you can sustain such powers.
Were you to have the wizard utility power Sleep, which is not an implement power, you would be allowed to use it while polymorphed.
I don't see a Polymorph power for wizards in the compendium, perhaps the name is different?
I would assume that the power you are referring to is a Polymorph effect. The effect says nothing about affecting spellcasting ability.
Unlike previous editions of D&D, there is no requirement for casters to have their hands or mouths free to cast.
Note that some polymorph effects do specify restrictions on using powers, but there is no general rule.
No - A spellcaster transmuted by Foe to Frog may not cast spells.
Now that the question has been clarified; Foe to Frog ddi reads:
[...]
Effect: As a Tiny beast, the target is dazed, and the only actions it can take are to move its speed or shift. [...]
Similar to what Simon Withers indicated is also the case for Slimy Transmutation.
