Eiru Fiscere caused me a great deal of trouble but here are accurate directions to them.
From Connla
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Leave Connla and head towards the bridge.
Cross the bridge and head North East following the riverbank.
Eiru Fiscere will be found on the hillside and in the trees just before the river branches.
From Howth
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Head South from Howth and cross the river at the stepping stones. Follow the river South East until you reach where the river branches. Cross the SMALL river and the Eiru Fiscere are in front of you.
Notes
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They are there Day AND Night time, and are agressive, though please be careful as there are Water Badgers close to the river.
They con blue/green to level 17