Due to shenanigans of my Dungeon Master, my character managed to get an Amulet of the Planes, but accidentally teleported into Castle Ravenloft while playing the Lost Mine of Phandelver. Can my character use the Amulet to leave Barovia, or is it stuck there until I finish that campaign?
If it helps, my character is a Level 4 Warlock.
Per the Curse of Strahd book (emphasis added):
Alterations to Magic
The land of Barovia resides in its own demiplane, isolated from all other planes, including the Material Plane. No spell — not even wish — allows one to escape from Strahd’s domain. Astral projection, teleport, plane shift, and similar spells cast for the purpose of leaving Barovia simply fail, as do effects that banish a creature to another plane of existence. These restrictions apply to magic items and artifacts that have properties that transport or banish creatures to other planes.
Note that the restrictions have nothing to do with the plot of the Curse of Strahd adventure, but rather the nature of Barovia and the Dark Powers that control it. Barovia is a prison and a deliberately constructed (emotional) torture chamber for Strahd: He always returns, because the Dark Powers will it. He always chases and always loses his love, because the Dark Powers will it. People can only enter or leave Barovia at the will of the Dark Powers, and only as instruments serving to continually punish Strahd.
In the original wording of your question, you made a couple of references to a "campaign". While sources like Lost Mine of Phandelver and Curse of Strahd are sometimes called "campaign sourcebooks", they are not "campaigns" themselves - they're sourcebooks for a campaign.
A campaign is a series of linked adventures, by the same DM (or a deliberately associated group of DMs, working together) with the same group of players. Your character hasn't transitioned from one campaign to another, it's changed from one setting (the Forgotten Realms) to another (Barovia, in Ravenloft). It's the same DM and presumably the same party, so it's all one campaign.
You can only escape if the Dark Powers choose to let you go. It has happened mostly to good characters that have fulfilled a specific purpose for the Dark Powers. But is very, very, very rare and their is not way to make it happen. If your character leaving would emotionally torture a dark lord, that would up the odds. Fall in love with one of the Dark lords. The only evil character that has ever escaped was Soth.
