
Baneblade is listed as "Sold Out Online" on Australian webstore
Commence panicking!

Commence panicking!
Converted from Soar Auxilia Veletaris, of course. Flamers are from Tempestus Scions, other arms are from Adeptus Arbites, Volkite serpentas are from the 30k melee sprue.
This question comes up daily so I'm going to post this and link back to it rather than copy-paste it every time.
First, watch this video (about 20 minutes): https://youtu.be/xF9uVsY9Fwo?si=aeCAfo4xfEZvvmDf
It's about 40k but it applies to all the Warhammer settings.
TL;DW: find a copy of an old core rulebook for the tabletop game, the first half of the book is intro lore. You should be able to get them cheaply from eBay or Facebook Marketplace.
Be aware that there are multiple "Warhammer" settings:
Warhammer Fantasy Battles AKA The World That Was is the original fantasy setting that eventually got discontinued due to poor sales, in a storyline event called "The End Times". This is the setting for the Total War Warhammer games. The Old World is set a few hundred years prior to the End Times.