It's surprising that there are 19 bosses even though it's a demo. Some bosses are lame and some are just skin changes, but the overall quality is very good. In most cases I used Flamberge +3~4 and also used the Obediah boss weapon.
Dark Souls: Archthrones
https://www.nexusmods.com/darksouls3/mods/1765
00:00 Demon Vanguard
01:07 Angel of Gertrude
02:24 Pus-Ridden Beast
03:27 Angelic Siege Golem
05:00 Omen of the Eclipse
06:44 Great Deep Accursed
07:47 Saint Klimt
10:24 Aldrich, Saint of the Deep
13:15 Carthus Sandworm
14:05 Chaos Amalgamate
14:55 Necromancer Obediah
18:10 Janara One-Eye
19:48 Silver Knight Captain Erdan
21:25 Rimeblood Hati of the Undead Legion
24:15 Kremmel, God of Struggle
28:13 Keeper of the Old Gods
30:02 Sir Florian & Warden Jessa
32:19 Disgraced Knight
34:13 Heide Phoenix