I'm a brand new DM about to start Tomb of Annihilation with my group. The party consists of four members: a druid, a fighter, a rogue, and a bard. I'm planning on giving each of them a fairly mundane magical item from Syndra Silvane as they are leaving Port Nyanzaru. The PCs do not know that these items respond to the user's abilities. The items are enhanced once they hit level 8, and again at level 16.
As an example, the Rogue will receive a Wooden Pipe, with Sylvan lettering engraved on the side. Once per day, the pipe can be blown into, and a cloud of smoke, encased in a bubble, floats out and moves 20 feet before popping. At level 8, this smoke bubble becomes one cast of cloudkill.
I'm worried that these items could become too powerful, but I've tried to curb this by only allowing them to be used once per day.
What are some potential issues that could arise from having these "evolving" magic items?
Best Answer
There are few problems unique to evolving magic items
"Evolving" a magic item is equivalent to taking away an existing magic item and replacing it with a more powerful one. Players are usually happy to get a more powerful version of whatever they have. In your specific example, a pipe that casts Cloudkill at level 8 is pretty balanced, since that's equivalent to a Rare item, which is level appropriate.
There are two potential issues I can see:
The low-level item is useless: I have tried to give fun but less-useful magic items to my players before, and they usually lose interest in them pretty quickly. If your starting item is too niche or useless, it's likely that it will become a forgotten line on the character sheet until it's upgraded. That's probably fine, but it sort of defeats the purpose of an item that changes over time. In the worst case scenario, they will get rid of it for something that they think is better.
Your players like the low-level item: Conversely, if your players really love the low-level item, and incorporate it into their character, they might be disappointed that their cool party trick has turned into an instrument of mass murder. You can solve this by allowing the item to be intentionally used at a lower level: i.e. a level 9 character can choose to only blow bubbles from the pipe if they want to.