Connacht contains 6 Mysteries in Assassin’s Creed Valhalla (ACV). This Assassin’s Creed Valhalla Connacht Mysteries Walkthrough will guide you through all Mystery Locations in the Connacht Territory. None of the Mysteries are missable. This region is part of Ireland in the Wrath of the Druids DLC expansion (DLC #1).
Mysteries get marked by blue icons on the world map automatically when synchronizing the viewpoints. Mysteries are side quests and other open world encounters. They include the following types: Cairns, Offering Altars, Trials of the Morrigan, World Events, Legendary Animals, Lost Drengrs. Finishing all Mysteries in Ireland is needed to complete all Territories for the Irish Legend trophy or achievement.
Also in this region:
Mystery #1: Trial of the Morrigan
Interact with the bowl and start the Trial, which involves defeating a wave of Druids. Nothing should really trouble you, although some of them like to breathe fire so try and take those out first with your Abilities and remember to roll with 
to put the fire out.
Mystery #2: Offering Altar (5 Deer Hoofs)
Deer Hoofs are obtained by killing deer and looting their bodies. A good place to find them is 300m to the south-west of the Altar in a meadow on the edge of the world map (shown in the screenshot below). There are lots of deer here you can kill from a distance with your bow and then loot them.
Mystery #3: Trial of the Morrigan
Interact with the bowl and start the Trial, which involves defeating a wave of Druids. This one is a little tougher as there are three Werewolves, so use your strongest Abilities on these and take them out first.
Mystery #4: Lost Drengr (Hogne Sea-Tossed)
Climb to the top of Downpatrick Head and speak to the Drengr. You’ll face him in one-on-one combat and despite being Power Level 449, he’s very easy if you’ve finished the main game and killed the other Drengr. Focus on parrying him to deplete his stamina so you can use a Stun Attack with 
for massive damage. Once he’s down, confirm the kill by holding 
to complete this Mystery.
Mystery #5: Cairn (Ben Bulben)
Stack the rocks to reach the required height and validate it by holding 
. This one is fairly easy with thick, wide stones, so it shouldn’t cause trouble unlike some of the ones in the late-game areas of the main game.
Mystery #6: Legendary Animal (Black Stout)
The Black Stout is a huge boar that loves to charge at you and ram you. Therefore, in this fight you’ll be dodging rather than parrying. Dodge its attacks and it’ll need to recover for a few seconds, giving you time to attack it. Hit the weak points on its legs to whittle down its stamina bar to do massive damage with a stun attack ( ). It is Power Level 453 but shouldn’t cause you any trouble if you’ve finished the main game and have a high Level yourself.
That’s 100% of the Mysteries you can find in Connacht Region of Assassin’s Creed Valhalla (ACV).
For all other Mysteries check out the complete Assassin’s Creed Valhalla Mysteries Guide. For the other Collectibles in this region check out the Wealth Guide and Artifacts Guide.
Anyone else having trouble with the first Trial of Morrigan? I’m getting the xp everytime it completes, but it never actually completes. I’ve tried resetting the game and console, with no luck
Same here, completed it 3 times, but it doesn’t show complete
Sounds like my problem too… No blue pins left for me in Connacht, but shows one left to complete “somewhere”…
I’ve found a few bugged mysteries in Valhalla… Lol