If you embark on the Volcano Manor quest, one of your tasks is to find and kill Juno Hoslow. That’s the final part of your mission to prove your loyalty to the group.
To get to Juno Hoslow, go to the Mountaintop of the Giants. You’ll find him at the Shack of the Lofty. The Red Letter that Tanith gives you shows the exact location of Juno Hoslow. Simply follow the red sign to get to the exact location.
Kill Juno Hoslow, get whatever he drops, and then return to Volcano Manor and talk to Tanith.
The trick to get to Juno Hoslow is to access the Mountaintop of the Giants area by progressing into the main story. Keep playing the main story before finishing the Volcano Manor quest and you should be able to get to the land of the Giants.
In other words, first, you need to progress the main questline in order to unlock the Mountaintop of the Giants area. Then you can complete the Volcano Manor mission and kill Juno Hoslow.
How to defeat Juno Hoslow
The best strategy to defeat Juno Hoslow is to use dual katanas or another weapon that inflicts bleeding damage. When he attacks, you need to quickly roll forward, deliver a couple of hits and then roll back. Wait for him to attack again and repeat the same pattern. Attack, retreat, wait, attack again.
Juno Hoslow often throws out only a single attack and then pauses for a couple of seconds. You can also try to block the first attack, come in for a quick counter-attack, go back and repeat.
You need to match the range of his whips if you’re trying to roll over him.
Juno Hoslow is a challenging enemy indeed. If you have a slow melee weapon, you won’t stand a chance against him. He spams whip attacks and bloodhound step dodges that render your attacks useless.
If you’re trying to attack him from afar, his whips will block the attack.
Be patient, learn his attack patterns, deliver a few hits, go back, rinse and repeat.
And now you know.