This thread is for info about the Hard-mode Van Darnus fight.
A quick summary of this fight is that you start out against Van Darnus' 2nd form.
Things to note:
• Once you aggro Van Darnus, he IMMEDIATELY goes into Megaflare stance. This means that no one will be taking any damage (except from falling meteors).
• Once you do approximately 2~5% of his HP in damage, he will use Megaflare
• Damage from Megaflare is approximately 5,000~6,000 damage:
- NOT affected by how fast you damage him
- NOT affected by what platform you are standing on when it goes off
- NOT affected by wearing Dalamud Horn and/or your Guardian Deity's ring.
• If you survive Megaflare, he goes back into his old routine from phase 2 of "To Kill A Raven".
• If you survive Megaflare, any meteors that hit the ground will turn into golems.
• Upon killing meteors and/or golems, they have a chance to drop Deaspected Clusters, which can be used to create the new Lunar Curtain item. Lunar Curtains grant a Sentinel effect (-50% damage).
• Sentinel is reported to stack with Lunar Curtain.
• Van Darnus is reported to use Megaflare again at approximately 20%.
• Van Darnus is reported to heal back to 100% when his HP reaches 11%, trollololololol
This means that in order to obtain Deaspected Clusters, you must first survive the initial Megaflare with your own power. Thankfully, all ability recasts are reset upon entering, so do not hesitate to pop your 15 minute abilities (mainly bard song for +HP) as needed. Don't forget about Sacred Prism + Sanguine Rite (if a THM can get to the bottom level in time) as another damage mitigation tool, along with Rampart, Sentinel, Stoneskin, and the like.
I do not know if Hallowed Ground protects against Megaflare.
Update: See post 20 for a full run-down of the battle.
XI Wiki



