A beardless mage (Zorin) in Castle Britannia told the Companions to visit the three castles and speak to all named Antos.
In the NES remake, in Skara Brae, we learn from his sister (Dickens) that Ramsel (Romasco) decided to brave the Abyss by himself; he can be met in Buccaneer's Den, and see how he failed the Quest of the Avatar and became a pirate instead. Thus, it is a ranger in Castle Britannia (Zair from Paws) who hints at the village of Cove, but the "Word of Passage" was omitted from this port.
Empath Abbey, stronghold of Love
The nearest castle is Empath Abbey.
In the NES remake, Brother Antos can be met in the secret passage. He directs you to "the village beyond Lock Lake".
Well then, how can we cross Lock Lake?
In the NES remake only, two inhabitants of Buccaneer's Den reveal the secret to reach Cove: the barkeeper (The Captain) and a pirate in the pub (J. J. Scirlock). Leave a 100 GP tip at the pub, and learn about the link between the whirlpool and Lock Lake.
The whirlpool moves randomly around the seas, but because of this randomness it generally remains in the same area. Apparently, it is more frequent to find the whirlpool north of Buccaneer's Den, south of Lock Lake river mouth.
In Cove, a bard in the woods (Paul McCartney) and a man behind the healer shop (Rabindranath Tagore) give the necessary clues to gather the Candle of Love. It is important to talk to the bard before getting the candle, or the Stranger will be considered a thief and lose virtue.
Mentorian (erroneusly rendered as "Mentallion") teaches the recipe for the "Gate Travel" spell.
In the NES remake the "Word of Passage", the "Axiom Riddle", and the magic ship wheel were omitted, therefore the corresponding characters in the castle (Joshua and Juliet) and in Cove (Spellbind, the Ankh, Allen) speak about other subjects.
Leave Cove, sail across the lake and leave the ship on the shore.
The Lycaeum, stronghold of Truth
The Lycaeum can be reached from the moon gate south of Trinsic. The moongate appears at the gibbous waning left-hand moon; its second destination (right-hand new moon) sends to Verity Isle. Travel north to the Lycaeum.
Find Father Antos and ask him about the Book of Truth. The Stranger will be redirected to the library. Jimmy the locked door, and search between R and V for the Book of Truth.
Serpent's Hold, stronghold of Courage
Serpent's Hold is on an island without any Moon Gate. The island is located to the south, but the shortest sea course to reach it is to sail straight north from Minoc.
In the NES remake, Sister Antos reveals all the information, but her information is incomplete: instead of being to the north, the Bell is to the north-east.
The magical ship wheel was omitted from the NES version. In fact, in this port, enemies in the wild are invisible until they engage in battle (except for pirate ships), therefore none of them shoots fireballs or cannonballs across the sea, therefore a ship's hit points are unnecessary, as well as the wheel that doubles them.