.monster
en.wikipedia.org.monster has been associated with spamming and phishing.
I block it on my firewall and my self hosted mail servers. Zero regrets doing so. All the TLD's that go for real cheap are instantly picked up by spammers and phishers. This is why we can't have nice things.
grep monster /etc/unbound/_*/*nxdom*conf
local-zone: "monster" always_nxdomain