https://maxroll.gg/d2/d2planner/buh3og0wHere's what I'm running. Easily one of my favorite builds. I wrote some info in the notes. I prefer Obsession+Flickering Flame (Current) over the Mang Song's+Hellwarden's (Old) version, mainly because of the resistances. Opens up your other slots to use whatever you want.
I really like Bind Demon, so I chose to max it and bind Hephasto; he's great for tanking and dealing secondary damage. Cursed and Holy Freeze for sure. Light enchant for better cursing or stone skin for tanking.
Rest of my points are just going into Blood Oath till 99.
Hex: Siphon is nice, but may or may not be necessary. Up to you. I like it personally. It will probably be mandatory if I ever switch to Infinity on merc.
I use death mark regularly for repositioning Hephasto. Engorge if needed. I use Sigil: Death to clean up herald minions then Lethargy for the main herald and bosses.
At lvl 20, sigils get their max radius (8 yards) so you have good coverage with 1 skill point invested. Holy Freeze from Hephasto + Sigil: Lethargy adds a lot of safety to your demons and merc.
I usually play on p1 when i'm being lazy or p3 when i feel like loading my two other accounts.
Gl hf