We are playing a very overpowered game (which is perhaps at the level of rocket tag), but is a ton of fun. My character is a 17th-level Zealot Barbarian (Xanathar's Guide to Everything, p. 11) and I intend to take him to level 20.
In the game, we are hunting liches and twice now the character has been mind-controlled, much to the detriment of our group's cleric.
Because of the high-powered nature of the game, we are regularly confronted with save DCs of 24 (or higher). Unfortunately, my Barbarian's Wisdom save is only +2, so there's no way for me to make the save. Advantage on saves is not an issue, but there still needs to be a possibility for success for that to matter.
Our party consists of a Zealot Barbarian, Storm Sorcerer, Thief Rogue, Divination Wizard, Light Cleric, and a Shepherd Druid. We are all 17th level.
We have access to just about any magic item. Furthermore, our house rule means that my Barbarian's zealot revival feature extends to reincarnation spells. It should be noted that to simplify the maths associated with reincarnation, the new form loses the old racial features and gains the new ones, but we don't change the ability scores.
With that in mind, are there any magic items that provide persistent long-term protection against mind control or a means to provide static boosts to Wisdom saves? Alternative means to increasing the likelihood of making a DC24+ save vs. mind control with a +2 Wisdom save are also of interest (this includes suicide and trying to reincarnate as something with better odds).