D&D 5E How did they decide on the mechanics of Polymorph?

[Quartz]

In the Monster Manual, it's very noticeable that anything that changes its shape retains it's hit points. In the PHB the various polymorph spells and abilities grant a new form with new HP. The shapechange mechanics seem much more sensible than Polymorph, so how did the designers come up with Polymorph?

 

[GX.Sigma]

Polymorph can be used offensively, so there needed to be a reason you couldn't save-or-die people by turning them into jellyfish or whatever.

 

[Parmandur]

Spells and monster abilities are not 1:1

 

[Thank Dog]

Given how brokenly overpowered it is, I'm fairly certain they used the "Pin the Mechanic on the Baa'tezu" method of decision-making.

 

[MacMathan]

Because they forgot the part in 3.5e where they threw up their hands and said it can't be fixed and forgot the lessons of 4e too?

In all honesty it should probably be two spells: Polymorph self and Polymorph Enemy so the save vs death aspect doesn't have to be balanced with the turning into powerful monsters aspect.

 

[UngeheuerLich]

Yes, polymorph self should work without gaining too many extra hp. Offensive polymorph should stay as it is now.
Actually, after reading, I am pretty sure, you can´t polymorph yourself with polymorph... I believe with the animal´s mental abilities, you can´t concentrate on spells. So we really need a polymorph self spell.

Note, that shapechange only gives a one time bonus hp. After the first change you don´t get anymore hp.
I however must admit, that the HP of a CR 17+ are maybe a bit much, even for a level 9 spell. CR equal to your level is also quite hefty, as a CR equal to your level means capable of holding out for a while against 4 characters of your own level...

 

[Riley37]

Hero System has self-only powers, usable-on-willing-subject powers, and usable-on-unwilling-target powers.

Polymorph Self, Polymorph Ally, Baleful Polymorph.

 

[Mephista]

They used the "You know, I'm tired of crappy players making us restrict cool stuff" method.

 

[Theovis]

Actually, after reading, I am pretty sure, you can´t polymorph yourself with polymorph... I believe with the animal´s mental abilities, you can´t concentrate on spells.

I'm pretty sure there's nothing in the rules to prevent spellcasting with Int 1, let along concentrating (which is based on Constitution).

 

[Plane Sailing]

Compare and contrast with Druid shape changing too