Ring of polymorph control
A ring of polymorph control is a type of ring that appears in NetHack.
Generation
Wizards may have a ring of polymorph control as one of the random rings in their starting inventory, though they will never start with the ring and a means of polymorph simultaneously.[1]
Description
Wearing a ring of polymorph control grants the polymorph control extrinsic: whenever you are polymorphed for any reason, if you are not stunned or unconscious and there is no applicable special case (e.g. polymorphing while wearing dragon scales or dragon scale mail), you will be prompted for the form of the monster you wish to change into, and you will never suffer system shock when doing so. However, there is still a 1⁄5 chance of polymorphing into your own species each time you polymorph, regardless of what monster form you choose with polymorph control.
If you have lycanthropy and would change forms while wearing the ring, you are given a prompt asking if you wish to do so; declining will leave you in your current form.
Strategy
Controlled polymorph has a nearly endless amount of applications for players, from eating jewelry to obtaining otherwise-difficult pets, to obtaining certain intrinsics and making travel easier, to gaining an edge in fights and overpowering otherwise-difficult hostile monsters. This makes the ring of polymorph control a valuable tool in almost any player's kit.
Identification
The ring of polymorph control is one of the safer 300zm rings, but is tricky to actually test for due to the dangers of random, uncontrolled polymorph - while it is much less likely to be cursed than a ring of polymorph on average, this should not be relied upon. If you are willing to take the risk, you can wear-test to rule out the ring of teleport control by putting it on and then activating a teleportation trap on or next to your square; you can rule out the ring of conflict by wearing it in sight of monsters that are near each other (e.g. a pet and almost any other monster). Testing rings for polymorph control becomes much safer and easier once you have the ring of polymorph formally identified.
The odds of a ring that is price-identified and tested for beatitude being a ring of polymorph control is given in the following table:
| Testing done | Any BUC | Non-cursed | Uncursed | Cursed | Blessed |
|---|---|---|---|---|---|
| Any price | 3.45% | 4.47% | 4.69% | 1.13% | 0% |
| 300 zm | 25.0% | 32.1% | 32.1% | 8.3% | -- |
| 300 zm, not telecontrol nor conflict | 50.0% | 90.0% | 90.0% | 10.0% | -- |
