From The Heroes of Might and Magic III wiki

This is a combination artifact.

Combination artifacts were introduced in the expansion Shadow of Death,
and are only available when it is installed.

Regenerates ALL of a hero's mana each day.

Requires the following artifacts to create:

• Mystic Orb of Mana
• Talisman of Mana
• Charm of Mana

You cannot purchase combination artifacts in Artifact Merchants. Cost is derived from sale price.

Basic Cost: 15000 gold

[edit] Comment

A fairly easily assembled combination. Do not carelessly split the individual pieces among your lesser heroes. My opinion is that this is more useful than the corresponding Spell power combination artifact Ring of the Magi.