So I was looking into magic items for my character to purchase when we made it back to the city in Tomb of Annhilation.  I am playing a Circle of Spores Druid (ruling that any undead I raise is flavored as more "Plant" just being the fungus that empowers me animating the corpse)

Nothing I saw fit very well, especially at lower levels of rarity.  So I thought about something that would fit well.  Tell me what you guys thing, especially about the appropriate rarity

The Soul Caller
Wondrous Item (magical War-horn)
Requires attunement by Druid, Cleric, or Bard

This war-horn can serve as a magical focus for the spell caster, and gives a +1 bonus to your spell attack modifier and spell save DC

This item has 1 charge, which it regains each day at dawn.  It can be used in two ways
it can replace up to 300 gp of material component (even if it would normally be consumed)

Or to cast the animate dead spell without expending a spell slot.

Any undead created or maintained by this item will become self-aware after 30 days.  Their intelligence and wisdom will become 10, and their alignment will be Neutral Good.

That is a very, very powerful magic item, probably Rare or maybe even Very Rare.

What's a good way to bring the power down, while keeping it's usefulness to a Spores druid?

Get rid of everything after the +1 bonus to attack & saves. That bonus alone puts it to Uncommon rarity, anything in addition to that is Rare or rarer.

Yeah, that's a good point.