[RPG] 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. Disillusioned by the leaders' willingness to send soldiers to their deaths, he has retired from the army and opened a shop. An adventure hook has people steal his work-in-progress masterpiece. I now need to find a fitting item that he was trying to create.

Because of this background, the item he would be most interested in would be something that helps ordinary soldiers (those who have no magic powers) survive the horrors of the battlefield. It can 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 would prefer to use an officially published item before resorting to homebrew (UA is probably fine, as is basic refluffing of a current item)
• The item must be below legendary rank – 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

The quality of an answer that fulfills these criteria can be judged by:

• How many people can receive protection or healing (either by number or by range of the effect)
• How often and for how long can this ability be used
• How powerful is this protection or healing (i.e. does it provide invulnerability, immunity, resistance, disadvantage, a bonus to AC or Saving throws and of what magnitude (here enumerated in roughly descending order), or in case of healing how many HP or temp.HP are provided, does it regenerate lost limbs and how fast)
• What kind of effect does it provide protection from, with higher value being things that are common on the battlefied and hard to defend against otherwise (saving throws are more valuable than AC, because mundane armour and shields can provide AC as well, protection against magic is usually of higher value than protection against attacks, protection against common AoEs like Fireball may be more valuable to groups of ordinary soldiers than protection against Finger of Death etc.)

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 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 and I need it to protect a group.