It's just Singed. Trolling as usual.
dark seal passive stacks on each other.
So if you have 3 dark seals and got 1kill, you get 6 stacks instead of 2.
No. Just no. Not even a little..
Dark seal's HEALING BOOST stacks with itself. Each dark seal makes potions heal 25% more. That+Some AP+Some mana makes it very cost efficient to any champ who uses a lot of potions(Like a singed). The Dark seal also has one of the best Sell-back values of any item, and probably the best out of the starting items? So you don't really lose much by buying them for lane, and ditching them later, IF you use a lot of potions.
http://www.nerfplz.com/2016/12/fotm-report-double-dark-seal-singed.html
Here is reliable enough insight and reason as to why this works and why it's good. 4 dark seals just doubles healing from potions and creates more lane pressure