Master Arcania is in the 'magic' section of Sepulchre East. That would be the 2nd down from the north or 3rd up from the south. The southern one is Lunayan and the next is Kolos. you want the one north of Kolos. Its the area that reminds you of Alra, with the 4 different mob colors / factions. light dark nature and arcane. Now that you are in the right section, the ph's for Master Arcania are [ Arcane magic caster ] and [ Arcane magic wielder ]. There are 3 of them. note there is no "an" before their name. The trash are an_arcane_magic_caster so thats how you can tell which are phs. One is on the platform towards the back near the relic and 2 others path on the north side between the light platform and the arcan platform. Master Ilium has 3 phs, but they are the Light magic caster types without "a" in front of their name. I will post this exact info under Master Ilium as well.
Forgot to mention, the phs are mezzable and stunnable. have just about 1 million hp. and hit me ( enchanter with AC approx 6700 ) for up to 12, 114 ( that was max hit one got on me).
So...we took a stab at this named last night....checked for a write up but didnt find anything, so we winged it....first attempt was a wipe...second attempt we took it down....didnt record the details but the named has a "drunk" aoe effect/w a knockback thrown in for fun...bottomline, make dang sure you clear mobs, face the wall and be prepared for a long fight.
I didnt see much of a knockback if at all. But i was levitated so... Im wonder if you play first person view which the magnification effect might appear to be a knockback.