So - dealing with Shadow Familiars in groups is a little buggy and kind of frustrating at times.
To join a group, you need to disband the group with the familiar before you can. If you do it this way, there is a lag in the familiar's movements - I suspect it's not joining the new leader's group.
You can avoid this by having the other party join you and then transferring leadership - then the familiar is in the group properly and can keep up. But this is also kind of a pain.
I wonder if it might be better for Shadow Familiars to simply not attempt to group up but have zero movement lag - so they can always keep up with their creator without needing to be part of the group?
Though that may cause issues with area effects, like the new Minor Haunting. I don't know. I'm just always missing joining groups because I miss the 'you're already in a group' message, making people wait on me to notice I missed it, and it feels like it makes grouping with me a little more unappealing.
Shadow Familiar Grouping
Re: Shadow Familiar Grouping
An alternative suggestion: Give them horse-grouping, where they're in your group but detach and attach to the group like a led horse does. This is a best of both worlds scenario (though... horses... have... certain bugs because of this feature.)
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