For resurected ghoul you must be lv 11+ to access it from Royal tomb/tomb of kings via accpting a quest from NPC there. (acceptanc eof qust is a one time thing, once done you can just enter instance back when it opens)
This one can be done in both group and solo, although it is poreferred you do in 2+ as you need quite a few things. This superbeing does NOT scale at all. therefore it will be same for a lv11 or a lv 18.
Whether you do solo or in group you will need a combination of the following. 1 slot of Charm Dispel, 2-3 slots of Antimagic, and 2-3 slots of Black clipse. This is why it is preferred you do this in group, espcially at lower mage levels, as after you have these MUSTS, you are left with few slots even if you have 10 slots total.
If you are in group, it is a good thing to do an understanding with your group before hand on who takes Black Eclipse, and who takes Antimagic, yet everyone SHOULD have 1 slot of dispel (for the effects and posisons you will have on you)
As soon as fight starts, you will need to Black Eclipse the Faz superbeing and its lv12 companion. these guys use the vamp spell so will heal for every dmg they do. Diffrence is, while the lv12 summon will only need 1 Eclipse, Faz will lose it few tims during fight. This is why you want 2-3 slots.
Now the antimagic aspect. Faz will use a magic that maks him stronger, and if it stays on long enough, it will summon more companions on his side. As soon as he uses this effect you MUST remove it. If in group, its best to decide order on when and who uses. If he accumulates enough effects on himself, he will sar one hitting everything (aka do 1000+ hits)
Mounts not needed if in group of 2+. If solo, all depends really.