Vladislavelikiy
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I've never made mods, but I'll say something. The summoned Phoenix and the regular Phoenix are the same creature; the only difference is that the regular Phoenix has standard stats, while the summoned one's stats depend on the hero and it doesn't resurrect. This means that if you change the regular Phoenix, you also change the summoned one. It's unlikely you can make them different, unless you use some workaround.
But where is the spell file located?