Arcane Mechanist's Core

This compact sphere or brass, crystal, and softly whirring gears is a marvel of Artificer ingenuity.  It fits neatly into your palm, or mounts onto armor, a belt, shield, or gauntlet.  Its modular design invites further improvement.

• Spellcasting Focus:  You can use the Core as your spellcasting focus for your Artificer spells.
• Toolform:  As a bonus action, you can cause the Core to reshape into a set of Tinkerer's Tools.  When in this form, it cannot be used as a spellcasting focus until returned to normal (bonus action to revert).
• Arcane Reserve:  Once per long rest, you can reroll a failed ability check made with Tinkerer's Tools, using the new result.

• Upgrade to Rare: Requires 3 days of work and materials worth 500 gp, plus the expenditure of one 2nd level Artificer spell slot each day of the upgrade process.

At the DM's discretion, special magical components might also be required.

Notes: Artificer