Difficulty:
ModerateBastion of the Triune (Profane Cells - Caldeum) Lucion's Soulstone
This can be a tricky uber at first but with practice its kinda fun. The most dangerous enemy here is the Temple Spires, which are randomly sprinkled throughout the uber. These totems can cast a meteor at your feet that kill in one hit. They typically cast 3 of them in rapid succession so keep moving and kill with 1-2 hits of Thorn Strike when its safe. Kraken Guards deal high cold damage but are easy to kill. Impaler Archons and Primal Clays are nothing special, just kill them. On to the boss stuff.
The boss here is Arihan, a fat creature that moves slow and can't be damaged directly. He casts a debuff randomly that can lower our life to 1, it lasts roughly 10 seconds. In order to damage him, he needs to hit by missiles from Primus' Messenger while charmed. Find Moca Loca in the Triune and kill to obtain the Tome of Possession. This tome grants + x to Dire charm which we won't be using because the duration of the spell is random, making it undependable. The tome also grants an aura which needs to be active in order for Arihan to take damage while charmed. This aura will disappear when you die so its very important to pick up the book and drop it back into the inventory after death. You can tell its active by the small green aura at your feet. This same aura will also be visible on Arihan when its active. Not re-equipping the book will prolong the fight unnecessarily so try to remember to do it. Instead of using Dire Charm, we will use Dominate, a skill that can be spawn on Druid helms. Any druid helm will work so use any shrines you can or find it on a rare. Dominate will last 20 seconds regardless of the skill level and the rest of the stats on the helm don't matter.
Clear out all mobs starting at the bridge, the courtyard (avoid the degen missiles from Primus' Messenger), and the building. Once everything is dead, lure Arihan out of his room and drag him towards the messenger. He doesn't need to be charmed right away just let him follow you to the doorways leading to the courtyard. I haven't quite figured out the deal with Arihan's AI. If hes pursuing you when you cast dominate, he will continue to walk in your direction until he touches you, at which point he will either stop or pursue nearby mobs, or he will pursue mobs if he is hit while en-route. Its very strange. So assuming you've made it this far, make sure the green aura is active, lure Arihan outside and cast Dominate right away and take cover behind a wall if necessary. Primus' Messenger casts degen missiles that lower our life very quickly. If debuffed by Arihan's 1 life spell, the missiles, or any damage for that matter, will kill instantly. Primus' Messenger will also summon a group of bats, which aren't that much of a threat outside Arihan's debuff and should be used strategically to keep Arihan moving in the Messenger's direction. Then theres the weird teleport field which the messenger also casts when he summons bats. This field can sometimes be seen as pulsing white novas on the ground. Walk too close and you will get teleported backwards or all over the place. The nova doesn't last too long so take cover from the degen missiles and wait it out. As far as using bats, try to kill only the ones that aren't between Arihan and the messenger. If they are close enough and Arihan pursues them, it increases the chance that he will get close enough to be damaged while charmed.
This is a video of a run I did a while ago. It took about 20 minutes once I started luring Arihan. There were a few times after dying that I forgot to re-equip the book, otherwise it may have gone a little faster.
P.S.
Remember to keep a portal open!