Sacred Nuts - can be obtained by defeating liphants. Liphants can be found in forest areas, especially in Arukas. You can carry a maximun of 11 nuts.
Staff of Earthquakes - can be obtained in a village on the island of Karme for $10,000 apiece. You can carry a maximum of 4 staffs.
Stone of Protection - can be obtained in a village near Iphis. Stones cost 50 fangs each. You can carry a maximum of 6 stones. (You will find a stone in Terarin's lair. This one will raise the maximum to 7 stones.)
White Sphere - can be obtained in a village near Dione (in Areos). Spheres cost 1,000 fangs. You can carry only one sphere at a time.
Resurrection Potion - can be obtained by defeating sea dragons. You will find sea dragons in the seas around Areos. (Note that killing sea dragons will decrease your character points by 100.) A resurrection potion will restore your character's life completely, but it must be used before your character dies. It will not bring your characters back from the dead. You can carry a maximum of 3 potions.
Mask - You can get the mask for $15,000 in the armory at Orcho (city).
Helm - You can find the helm in a monument near Julus.
Mantle - You can find the mantle in a monument near Silvius.
Crystal - You can find the crystal in the monument near Silvius (same as the mantle). To get the crystal, you will need to read the inscription on the cave wall (for which you will need the helm).
1st boat - After defeating the skeleton, you can go onto the peninsula of Kadamos. You can get the boat for $30,000 in a village in the open area. (You will need Guy to get onto the peninsula as Guy seems to have a distinct advantage when fighting the skeleton.)
2nd boat - You can get the second boat in a village on the island in the northern lake of Apheidas. You must have Treo with you to get this boat.
Money - You can carry a maximum of 600,000 guilders.
Swordsmith - you will find a swordsmith in the town of Orcho who will come with you for $12,000. He will prevent your weapons from breaking.
Guy - Guy can be found in the city of Kadia. (Kadia is not on the map; it is near Baton.) You will need the sword Iris before awakening Guy.
Medi - Medi can be found in the town of Doris. You will need the Kronos armor before awakening Medi. You will need Medi to unlock caves.
Treo - Treo can be found in a cave on a small island in a lake near Iphis.
-- When you get a new character, his/her life meter will be one level less than the life meter of your weakest character. However, there is a maximum life meter length for new characters, after which point, their strength must be increased through battling enemies. (I.e., do not spend all your time in building up your characters excessively in the hopes that you will not need to build up the new characters.)
-- Besides the swords, Kronos and Ulysses are the only two pieces of equipment in unlocked caves. Everything else is in a locked cave. Locked caves can only be opened by Medi.
Miracle Warriors Guide
An excellent source for more information on Miracle Warriors.