Yeah, I've looked everywhere but if you'd like to look yourself it's "Saint-elme" tome 5 (volume 5) by Lehmann and Peeters.
All 4 first books are on Anna's and elsewhere but tome 5 was published fairly recently (January) and a French forum sharing bande dessinées has a "6 months rule" about sharing newly published works (honestly I don't understand why but who am I to discuss their rules) so it will be available at some point but since vol 5 is the last one, I want to read the end now.