PC as equivalent CR creature

[Totema]

I'm trying to size up for myself how powerful polymorph spells in this edition are, compared to how they were in previous editions. It seems like they tried to balance it by restricting the CR of beast you transform your target into by their level, but the problem is, CR scales incredibly faster than levels do. A 20th level wizard transforming him/herself into a CR 20 creature using true polymorph would be able to end a deadly encounter alone.

But that's a different point. I'm not trying to debate the strength of polymorph, there's another thread for that if I recall. :smalltongue: I'm just wondering, as part of my analysis of the polymorph spell family, what CR would a player character in 5e have if they were statted like a monster?

[Inevitability]

A 20th level wizard transforming him/herself into a CR 20 creature using true polymorph would be able to end a deadly encounter alone.

Could you give an example? I'm kind of curious.

Also, they are 20th-level wizards, literally the epitome of magic-users, using one of the mightiest spells in existence. Beating a deadly encounter is strong, but kind of expectable.

[MaxWilson]

I'm trying to size up for myself how powerful polymorph spells in this edition are, compared to how they were in previous editions. It seems like they tried to balance it by restricting the CR of beast you transform your target into by their level, but the problem is, CR scales incredibly faster than levels do. A 20th level wizard transforming him/herself into a CR 20 creature using true polymorph would be able to end a deadly encounter alone.

But that's a different point. I'm not trying to debate the strength of polymorph, there's another thread for that if I recall. :smalltongue: I'm just wondering, as part of my analysis of the polymorph spell family, what CR would a player character in 5e have if they were statted like a monster?

Based on the idea that a Deadly encounter should have only a chance of proving fatal to one or more characters, I would deduce that a mirror-image party should rate beyond deadly. Let's guesstimate that the mirror image party is twice as much XP as the Deadly encounter budget. That makes 3rd level PCs approximately CR 3, 7th level PCs approximately CR 5, and 17th level PCs approximately CR 12. If you think I'm underestimating the mirror image party's deadliness you could renormalize and recalculate.

Also, CR are a bad metric anyway, and my rough guesstimating makes the situation even worse. Where possible, try to avoid using CRs for things that have class levels, it will usually give worse results than eyeballing.

[Shadow]

There's no real way to build a metric for it without specific example of the character in question.
The more special abilities/attacks or spells a creature has, the higher the CR is.
Just looking at the NPCs listed in the MM will show you what I mean.