Which magic item of very rare or lower rarity is most useful to protect a group of ordinary soldiers?



Background

I’m playing a mid-level artificer (artillerist) who’s a disgruntled veteran with a missing limb who, disillusioned by the leaders’ willingness to send soldiers to their deaths, has retired from the army and opened a shop. An adventure hook has people steal his work-in-progress masterpiece and now I need to find a fitting item he was trying to create.
Because of this background, the item he would be most interested in would be something that helps ordinary soldiers without magic powers survive the horrors of the battlefield. It might be something that protects a group of people from hostile spells or something that provides healing to them, similar to the artificer’s Protector cannon.

Criteria

  • I am trying to find an officially published item before resorting to homebrew (UA is probably fine, as is basic refluffing)
  • The DM has ruled that the item should be below legendary rank, so very rare at most
  • I probably won’t be held to strict prerequisites such as being able to cast every spell going into the items myself, but the item should still basically fit the artificer flavour
  • The item should be usable by someone who cannot cast spells
  • The item should be able to affect a group, not just the carrier
  • The item should be defensive in nature

My own research

I’ve gone through the "warding" and "healing" categories of magic items on D&D Beyond and found very little. There are almost no items that work on groups and those that do tend to be musical instruments or magic staves that need the user to be a spellcaster.
In general it seems that antimagic items aren’t really a thing in 5e. An item that can cast Antimagic Field on he regular would probably be in the legendary category and a Ring of spell Storing would again require a (powerful) spellcaster to be useful.
An ideal solution would be something like a banner of protection or an Eldritch Cannon: Protector that doesn’t need an artificer to be present. I’ve also considered something like a Ring of Regeneration, but that’s again a one-person item.