I did some testing with the Invoker of Death at +7 and +9 with variations of cards, My findings showed that it works best with a hybrid crit high atk build with Kaahi buff and Proxy Skin Fragment to supplement the sp drain, I don't recommend this build if your solo, it works best if you have a HP nearby to keep you assumptio and healed comfortably, because if you get hell debuff you won't be able to resurrect until it times out.
kaho and Valk upper with gryphon is variable depending on the place your farming at, usually you want to go with kaho tho for the raw damage. mid is always str+1 Gryphon.
Lower is completely optional, but you'll see a better comfort zone with the Pussy Cat Bell, if you don't have that tho Chewing bubble gum works well.
Armor is variable
Invoker of Death +7 (+9 is not needed at all) Dopple and Bapho cards provide constistant results.
Proxy Skin Fragment (usually with Deviling card)
Shoes are variable but I used Lady Tanee Sleipnir
Accessories I got the best results from were holding at least 1 Meg, but if you can supplement the build with crit by taking 1 accessory with Ifrit card that's where I saw the best results. If your targets have under 30 defense tho you'll be better with raw str from dual Megs.
if your relying on crits for high defense targets you'll want to farm up some Arunafeltz Desert Sandwich in bulk to take with you. And change the build into double bris~Ifrit and Valk~Gryphon
all in all this build is a bit of a meme, but it does have its merit and is very strong for what it offers and is probably the optimum build for an auto attack build in terms of consistency and power so long as you have support with you. With that being said, i tested it in juperos and Geffenia. Juperos was a cake walk and geffenia got a bit rough with the sp problems. But when I had sp it was extremely brutal and wiped out everything like a lawn mower.
Here is a rough build to alter depending on what available resources you have at your disposal. https://calc.talonro.com/?_w43CikEOwoIwFAVPwoXCrE0IQcKsCxIvMMK/w7bCt8OYwogswpTChsObw7NZcAdmM2/CksOnWcOEw4koDV/CucKxIMO0w7cXw4w5McOww4QIFQcpQxlDU8OaacO1w7Vvwo5Fw5/DkcOpA8OUwqULIcOBJ8ObJ0dVw4zCssKHccK1acOyw789OsOOw4MG