There are several militant orders known about that have intershadow influences.
Knights of the Sword – small reputed vampires – had spat with SS in WWII.
Templars – Knights of the Temple – (think Holy Blood Holy Grail version in spite of some debunking it is good for story telling) – Found in different shadows and still exist on some openly. Templar golds travelled through shadow reportedly.
Neo Templars – Some good, some bad. Claims to be Templar successors.
Hospitalars – Still have ties to RCC – Knights of Malta in some shadows.
Teutonic Knights – Became Junkers with Reformation in some places. Other places still exist.
Knights of the Broken Sword – Templar connection – not much known
Knights of the Cross Swords – Alcazar’s and Tone’s Dad’s Group. Halves of the Golden Apple issue. Warred with Lucius.
Jedi/Sithe – Reported in SF areas. Not much known. Involved in Caine/Thrawn SF worlds war
There may be others including one former group fighting Gaius’ lords in shadow with pirates in shadow.