Your "main" Galakrond isn't cleared when the card is destroyed or transformed
https://us.forums.blizzard.com/en/hearthstone/t/discarded-enemy-galakrond-but-still-invokes-are-effectiv/20326
I discarded the enemys Galakrond but still invokes are affected.
More hilariously:
https://us.forums.blizzard.com/en/hearthstone/t/galakrond-transmogrifier/20809
https://imgur.com/xUbxhym
In the above video, before the Galakrond is trasformed, Dragonblight Cultist summons two 1/1 imps. However when the Galakrond is transformed into a shaman minion(Al’Akir), Dragonblight Cultist triggers shaman Galakrond’s hero power.
It seem quite weird that warlock doesn’t control any shaman Galakrond but invoke card triggers shaman Galakrond’s hero power.
Also if Galakrond transform into neutral minion or non-Galakrond class minion, invoke animation is still pops up when you play invoke cards but it doesn’t trigger any hero power.
Per the explanation here, destroying or transforming it should clear it: https://playhearthstone.com/en-us/blog/23190444
Once determined, your main Galakrond remains the same for the rest of the game unless it’s destroyed, transformed, or you replace your Hero with a different version of Galakrond.