Looks like Katy Perry isn't the only one Taylor Swift has bad blood with.

After apologizing to Nicki Minaj last week following their testy MTV VMAs Twitter exchange -- which incited a shady response from Katy Perry -- it appears it's now open season for other artists to come out of the woodwork to challenge Taylor. Surprisingly, her latest adversary is Edward Droste, frontman for the indie-rock group Grizzly Bear.

It all started back in February, when Droste tweeted about a "terribly calculated and mean" celebrity, though the tweets have now been deleted. "Met a celebrity I always speculated was terribly calculated and mean, and they exceeded all my expectations of rudeness and arrogance. HATE" Droste wrote.

WATCH: Nicki Minaj Says Taylor Swift Apologized to Her Over the Phone

But he was also afraid of the celeb's obvious power.

"If you know please don't @ the person, they see all and have the capacity and desire to destroy, seriously, please just know and lol. ... This is an eternal blind item, bc I'm too petrified of their insane power. No need to speculate, just HAD to voice my disgust."

On Sunday, Droste pretty much confirmed that he was referring to Taylor, when he tweeted a picture of a report titled, "Mean Girl Taylor's Friendship Rules!" The report claims that the 25-year-old "Blank Space" singer had strict rules to make sure her celeb pals like Kendall Jenner, Gigi Hadid and Karlie Kloss didn't upstage her when she brought them up on stage during her Hyde Park stadium show.

"Taylor had a dress code for everyone to make sure she wasn't upstaged," the report reads. "And they were all told to stand a certain number of feet behind Taylor at all times, not to speak unless spoken to, and not to discuss Taylor's private life in interviews."

Droste commented, "Obsessed that people are catching on."

He then retweeted a Billboard article about Taylor's lawyers threatening her former guitar teacher with legal action over his website name, but perhaps most tellingly of his feelings about her, retweeted a particularly harsh message reading, "I want to just put out here that I've always known Taylor Swift was immensely evil as she is powerful."

Ouch.

WATCH:Kelly Clarkson Covers 'Blank Space' and Taylor Swift Loves It!

Taylor has yet to respond, but she did make headlines at her recent 1989 World Tour stop in Foxborough, Massachusetts over the weekend when a "left shark" came on stage -- which some saw as a dig at Katy Perry.