Is Gunther evil, or has he some kind of plan, because in previous episodes i thought he´s just acting like a spoiled child, but he seems to have somekind of thing going on, like manipulating the cosmic owl to show her PBs dream so she could destroy it. Also will PB die, she died in her dream and cosmic owl was in it so it will be bound to happen.
It seems like Gunter seems to have evil motives from time to time, like your example, as well as in “Reign of Gunters” when s/he cloned her/himself with the demonic wishing eye in an attempt to take over Ooo.
As stated by Hunson Abadeer in “It Came from the Nightosphere”, of all of history’s greatest monsters, Gunter is “by far” the most evil thing he’s encountered. (This point is debatable considering Hunson might have been trying to trick Gunter into giving up his soul by choice. I’m not for sure.)
Gunter’s not above doing bad things for her/his own personal benefit, like stealing the demonic wishing eye and breaking people’s bottles for her/his own enjoyment, even going so far as to attempt to shatter the head of a Gumball Guardian. (Essentially one giant bottle.) - Alisyn
As for your question about the cosmic owl he stated himself that his presence in a dream will cause the events in it to come true. ~Alex