This is my guide on beating the PUPPET MASTER!
#1. Relics
The best Relic to use is the Ancient Astral relic as has a Astral spell and Astral beats Shadow. If you do not have it, try the Ancient Storm. If you do not have that, use a relic that has a spell with high damage and low recharge (it does not matter if the aim is random.) I used the Ancient Storm relic,.
#2. Equipment
Use your best armor. The best set to use (the best in the game actually) is the Titan Power set. Mira's set is also very good. I used the Celestial Set.
#3. Wands
Your best bet is the Cosmic Sword. If you do not have that you may purchase the Dual Blade and use that as it also has a good Astral spell. Do NOT use wands with Physical spells. I used the Dual Blade.
#4. Pets
Use high-level pets with good health and damage (don't be overkill on damage.) Do not use pets like Shivertusk as they have too many Physical spells, and Physical is weak to Shadow. I used Embershed and Fathom.
I hope this helps!