okay another wild guess...Inferi???
coz unlike dementors, inferi can be seen both by muggles and wizards...
it does freak out anyone who they make their target...and anyone else who sees it becomes curious or quizzical about its existance...
beginning of the end...the end was the hunt for horcruxes...inferi came out in the cave where harry really intentionally began the hunt...
triggered by the water...forced the trend of drowning ppl...
it cud give a good defence to voldemort...
and it seemed that there were actually no limits on which they could spread...
a few powers can blind me...i dont exactly remmeber what i read in HBP..but the pamphletss issued by the ministry said something about ways to keep inferi away..maybe light or something...
and it can definitely get in its surroundings...
uff...my wild guesses...
or...Goblet of Fire???
made everyone quizzial n curious and freaked out harry oon announcing his name...
beginning of the end...the end was voldemort...when his re-existance came to begin...the goblet came out then...
ofcourse its very powerful...and the danger ahead of it is limitless...
a few powers like barty crouch jn.'s dark magic could hoodwink it...
or...wait...*eyes widening in shock*
MAGAZINE!!!
that..Luna's father one...the Quibbler!!!
magazines dwell in both worlds...
the funnyness and absurdness of it makes ppl curious n quizzical...(the freaked-out way they used to stare luna when she used to read it upside down)
the beginning of the end...the end...the battle of hogwarts...they were on their way back when they visited Xenophilius and saw that he was printing the magazine against potter...
triggered and forced a trend...when hermoine told(triggered) rita n luna to get harry's interview about the dark lord's return printed...and umbridge was against it...the trend started to tear the interview pages and put a charm on them to make them appear blank...
harry was unable to defend himself...but by the magazine and its power, he won a lot of trust...
there seemed no limitts to which it wud continue...
few powers that cud blind it...the death eaters' power (they kidnapped luna) blinded Xenophilius and started printing against Harry...
but it can always get into any surroundings...afterall its a magazine...