If a custom mob uses a skill that summons a mob into the battlefield, it will not gain its proper stats or level. Example of using Summon Unkindness below:
Chaos Calling works fine, strangely enough...
This is specifically for Summon Unkindness. It's because it's currently programmed in a way that only makes them scale to level if it's used by a random dungeon Winged Guardian. I have adjusted it so that it will only use the level 10 version if it's used by the static Winged Guardian encounter.
Be careful about making wide-reaching assumptions about bugs, because it can potentially lead me on a wild goose chase.
Just for clarification, but is it intentional that Calling Tone and Seeker Flame's summoned unit's stats turn out this way then?
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They turn out that way regardless of an AI mob or controlled mob summoning them.
No, but that is a separate issue and has been corrected.