[Spell] Metamorphosis with changing leveling spells

[Nevanii]

I made a metamorphosis spell based off Illidan's one (permanent one) and gave it to my TreeHero. The idea is that metamorphosis unlocks at level 5 and turns TreeHero into CorruptedTreeHero. I want him to have different skills that he'll be able to level up (He'll also have metamorphosis spell to come back to his normal form with NORMAL spells). For now when he enters metamorphosis he still has same skills, and when I preplace him in corrupted form, he has the spells that his CorruptedTreeHero form should have. So it's all in the metamorphosis skill, and I have no idea how to make it. (I'm on 1.27 legacy version, couldnt open maps from other threads since they were on newest ones)