Ultima IV: Quest of the Avatar/Side Quests

All information to get the rare items is already in the game, if the Stranger talks with every character. Although the NES version has simplified dialogues, most information is still found in the same towns and also at the same pubs.

Shepherd items (NES only)
If you are playing the NES port, and in particular if you are playing as the shepherd, this is the first side quest you will do.

In the NES version the party can include up to four companions, while the other ones can be left at the hostel in Castle Britannia. Because of this, some items were created to upgrade two characters (the shepherd and the fighter) considered weak, otherwise players would have seldom used them.
 * The sheep flute for the Shepherd: it allows to cast "Sleep" on all opponents unlimited times with no MP consumption;
 * the humble robe for the Shepherd: it is one of the best armor in the game, only inferior to the Mystic Armor;

The flute and the robe are found in Magincia ruins. First of all, you need a companion who can cast the "cure poison" spell, then you also need to purchase the magic key that costs 2000 GP. In other words, if you are playing as the shepherd, it is impossible to obtain these items since game start. When you come back to the ruins, talk to the skeleton in the north-east, and it will give you permission to take them (otherwise, your virtue score will be lowered). Both items are in chests, in two different basements: the flute is at the centre of the ruins, and the robe is in the south-west.

Mandrake root
As the Nightshade fungus, Mandrake root can only be found "on the darkest of nights".

Seven spells require Mandrake root:
 * 1) Jinx: useful against large numbers of enemies;
 * 2) Negate: useful against enemies that cast debuff spells (sleep) on the Companions;
 * 3) Resurrect: absolutely necessary, although hopefully used not often;
 * 4) Gate travel: use sparingly, because walking allows to fight and earn experience and gold;
 * 5) View: useful, but it's more convenient to buy magic gems instead;
 * 6) Tremor: not useful, ranged weapons are more reliable;
 * 7) Iceball: not useful, ranged weapons are more reliable.

Nightshade fungus
Three spells only require Nightshade fungus:
 * 1) Jinx: useful against large numbers of enemies;
 * 2) View: useful, but it's more convenient to buy magic gems instead;
 * 3) Kill: not useful, ranged weapons are more reliable.

Original spell quests
This spell requires garlic and sulphurous ash.
 * Undead

🇨🇴

Improved spell mixes
🇨🇴
 * quickness
 * sleep
 * magic missile

Master System spell quests
🇨🇴
 * quickness
 * sleep
 * iceball

NES spell quests
In the NES version, there are more spells to be found: sleep, reflect, negate, destroy, jinx, squish, tremor and defeat.

Legendary axe (NES only)

 * The dragon scale to create the legendary axe for the Fighter: it is the second best melee weapon in the game, only inferior to the Mystic Sword.

The scale is found in the Serpent Spine mountains, that can only be reached by air. If it's brought to Zircon of Minoc, he will use it to create the legendary axe.