Here is info about the SoS end boss (Sorjec). We need to kill him to get a chance for a sovereign rune.
Type: Undead
Race: Lich
Alignment: Lawful Evil
Boss: Purple Named - Powerful Boss
Special Qualities:
◦ DR: ♦15/ ♥~30 / ♠50 /Bludgeon + Magic
◦ 100% fortification (but can still be crit/sneak attacked by using various effects which lower fortification)
◦ Low Fort save (Disintegrate works well), moderate reflex save (Fireball works well), high will save.
◦ Immune to Lightning and Cold damage
◦ Various buffs based on his mephits - See below
He gains additional abilities as he summons mephits [1]
◦ Dust Mephit (Lammania) - DR/-
◦ Ice Mephit (Risia) - very strong cold version Fire Shield, ~50-70 damage/swing, greater cold resists won't cut all the damage
◦ Fire Mephit (Fernia) - Significant Health regeneration
◦ Air Mephit (Syrania) - Haste
Recommended Weapons
◦ Greater Undead Bane blunt weapon (best with decent prefix, like Holy, Anarchic, Flaming, Acid, although ones lacking a prefix will suffice)
◦ Blunt Greensteel (any with holy/fire/acid damage should do fine)
◦ Triple Positive (Holy/Good Burst/Good Blast/Greater Disruption) weapons are by far the highest dps for him.
Note that there are no Greater Bane weapons for mephits, as they are Neutral Outsiders and neither Elementals nor Magical Beasts.
Recommended Strategies
◦ Sor'jek can be moderately effectively surrounded and kept in one place by 4 or more durable (500+ hp) characters. He can force his way out via knockback attacks, but doesn't do so often.
◦ While locked in one general area, persistent AoE damage spells like Firewall are quite effective. ◦ They can be equally effective when soloing by simply circling him, or in a group by simply holding agro. He will not pursue his target, he has caster AI and thus will simply lob spells at ranged attackers.
◦ Many groups assign one (or more) players to kill all mephits on sight while the rest damage Sor'jek and try to hold him in place. However, the Syriana mephit can be completely ignored if desired.
◦ Mephit spawn rates seem to increase over time, but only one of each specific mephit will be active at one time.
So the key is to have blunt weapons to bypass his DR 50 (on elite). Fortunately I crafted a triple positive Greensteel Maul just to deal with Sorjek and other undead.