D&D 5E Can I Polymorph myself?

[Ginger Ferguson]

Animals, cr 1 and below, aren't very combat capable. Low Ac's, low damage output, etc. What are some good reasons a 10th level wizard would polymorph itself?

 

[Cap'n Kobold]

With a scroll you still need to maintain Concentration, but with a potion the spell is entirely self-contained. (Spell scrolls are like "partially cast" spells, and you complete the casting as you read it from the scroll.)

I don't believe that your comment about potions is correct. A potion that allows you to cast a spell still does require concentration, unless it explicitly states that it doesn't.
You might have been misled because some of the potions in the DMG don't require concentration. However this is either because they outright state that no concentration is required, or because they just give you a capability rather than cast a spell. (Such as the potions of Flying or Invisibility.)

 

[Eis]

Animals, cr 1 and below, aren't very combat capable. Low Ac's, low damage output, etc. What are some good reasons a 10th level wizard would polymorph itself?

primarily movement types and camouflage....you're a dog and can pass unnoticed through the city or you are a spider and can climb a wall and hide....not everything has to be directly combat related

 

[jgsugden]

1.) Yes you can polymorph yourself and maintain concentration on the spell. No special skill or ability is required to concentrate. Any creature can concentrate.

2.) You can't cast spells when you polymorph into a beast because you replace your game statistics with those of the beast - meaning your class abilities, including spells, have been replaced when you cast polymorph on yourself. Class abilities, including spells, are game statistics. You don't have spells to cast, so a question of whether the beast's statistics are sufficient to cast a spell is irrelevant, generally.

An 8th level wizard can polymorph himself into a T-Rex and attack enemies - so long as he maintains concentration. If he gets hurt, he uses the T-Rex ability scores to determine his Con save to maintain concentration. It doesn't matter what he is proficient in when in his normal form - his game statistics in the T-rex form do not care about what he is proficient in normally. He can't cast spells as T-Rex do not have spells and his game statistics are limited to just those of the T-Rex.