question regarding ignite and a build Im following

hy,

Im following this guys build...

https://poe.ninja/poe1/builds/mirage/character/kittikhao05-6971/ZTMZT?i=2&search=class%3DHierophant%26skills%3DSpark%2Bof%2Bthe%2BNova

I am level 98 and I am there, for 95%

But He uses a flask wich trigger healing and damage by killing ignited enemys.
But I don't get where he gets his ignite from...

I tryed the flask and it pops allot, so I must be consuming ignited corpses and igniting enemys.

Please explain

thank you