The 5th level party I DM for just found a Hat of Disguise. Our Rogue (Thief Archetype) is fascinated by the endless possibilities, but slightly put off by the shortcomings of the Disguise Self spell it casts. She has had a conversation with our spellcasters, and her player has asked me whether they could find an item that would cast the more powerful Alter Self spell. I see much potential for entertaining mayhem in this.
Is there an item that casts Alter Self, say, once a day? Even homebrew? (If I can't find anything official, I'll homebrew it anyway.)
I have skimmed through the DMG and only found the Wand of Polymorph, which isn't quite what we had in mind. The Infiltrator's Key is way overpowered for this.
Best Answer
Based on a search of all magic items available in D&D Beyond, the Infiltrator’s Key from The Explorer’s Guide to Wildemount is indeed the only official magic item that casts alter self.
There are probably plenty of homebrew items that do - I found this ring of alter self on one of the many D&D wikis. It confers one specific, personalised application of the effects of the spell while worn, and the effect becomes permanent if it is worn for 30 days.
That may not be quite the effect your rogue is after if they enjoy the spell’s versatility, but as the spell is only second level an item that can cast it once or even a few times a day should be easy to create without too many balance problems.