They are initially friendly and will cast their spells on either team, similar to Danika during the Raisu Palace mission.
After you have talked to Razah in the Heart of Abaddon, they will turn hostile on your team. They have a lot of Health, but they will stop casting their healing spells and their attacks deal no damage, so they are safe to ignore.
Their attacks do, however, trigger Painful Bond.
Binding Guardians do not appear to drop loot.
Binding Guardians have continuous Health regeneration.
Unlike most spirits, Binding Guardians are vulnerable to the Deep Wound condition.
If you use Gaze of Fury before you talk to Razah you can avoid having to kill them later and avoid their spawns.
If you use Signet of Binding after you talk to Razah you can bind them to you.