Must have already acquired Thurston's Fort,
Speak with Old Thomas to trigger Secrets of Mithril.
|"Mithril can be found in Dark Caves"|
SECRETS Of MITHRIL
Send your knights to (Adventures) "Explore the Dark Caves" AND
Acquire 1 Mithril
⛔WARNING: Send your knights out AFTER the quest is triggered for it to count. Mithril must be IN your inventory AFTER the knights return to complete the quest. So, to avoid an additional Mithril hunt, wait until this quest is over before crafting the sword⛔
Now you are ready for Forging Excalibam.