I've done all the 125 ubers with my UMP using only Lemures except Xazax and upgrading the Dragon Claw which I used Winter Avatar for.
For Astrogha, you can Divine Apparition in and hit him with 1-3 Lemures depending on time before he summons towers or teleports away. Then you get out of range until it doesn't show his health meter, wait a couple seconds and repeat until you down him.
Bremmtown is really rough with Lemures so I used Winter Avatar from
Shiverhood
Shiverhood
Full Helm (Sacred)
Defense: (3596 - 4141) to (4218 - 4803)
Required Level: 100
Required Strength: 300
Item Level: 105
You may Only use Melee, Summon and Support Skills
+(1 to 2) to All Skills
+(20 to 30)% to Cold Spell Damage
-(15 to 25)% to Enemy Cold Resistance
+(15 to 20) to Winter Avatar
+(25 to 50)% to Summoned Minion Life
+(120 to 160)% Enhanced Defense
+(600 to 1000) Defense
Maximum Mana +(10 to 20)%
+100 Life on Melee Attack
Requirements -50%
Socketed (4)
to get to the dragon in time. You could also use
Frostneedle
Frostneedle
Kriss (Sacred)
One-Hand Damage: 39 to 40
Required Level: 100
Required Dexterity: 454
Item Level: 105
Dexterity Damage Bonus: (0.11 per Dexterity)%
You may Only use Melee, Summon and Support Skills
2% Chance to cast level 19 Glacial Nova on Death Blow
+(1 to 2) to All Skills
+(25 to 40)% to Cold Spell Damage
-(15 to 25)% to Enemy Cold Resistance
+(20 to 25) to Winter Avatar
Maximum Cold Resist +(1 to 2)%
50% Bonus to Defense
Cannot Be Frozen
Socketed (3)
or both together.