[RPG] Is it possible through established game mechanics to extend the duration of Alter Self to 12-24 hours


I have a Crowley-esque character (the demon from Supernatural) who is concerned about ehem certain features, and this is exactly the kind of petty nonsense this character would do. I'm looking for a way without endless scrolls that the duration of Alter Self could be cast only once or twice a day, preferably that could take out the concentration component as well.

Best Answer

The closest you can get is with the warlock invocation master of myriad forms, that lets you cast alter self at will. It still requires concentration and you have to refresh it every hour. It also needs you to have at least 15 warlock levels.

If levels are at a premium, but only the illusion of a different shape is enough for most of the time, you can go with mask of many faces, that requires only 2 warlock levels and lets you cast disguise self at will. If you take another 3 levels in sorcerer, you will be able to sustain alter self for 4 hours with the extended spell metamagic.

If you are the DM making an NPC, I recommend you just grant them the spell at will or base them on a shapeshifter fiend. It is unlikely to unbalance anything and might add nice flavor to the character. Also, neither at will low level spells or shapeshifting is rare in fiends, so you could consider it an "established mechanic". As far as that can go for a custom NPC anyway.