"We are going to conjure the spirits," she told the town hall audience.
The crowd acknowledged the occasion with an impromptu version of Happy Birthday, to which Lorde responded, "thank you so much".
She said she was ''too scared'' to do a yardy [yard glass], but would ''do a shot'' later.
She said it was still "a big deal" to be in Dunedin. When she started out a long time ago she was "scared" about how big the town hall was, but it seemed ''a lot smaller'' now.
Superfan Isaac Rijlaarsdam, 17, said he and friend Beth Moody, 16, were first in line at 5.30am for the 8pm show.
''We wanted to be at the front, so we played it safe. Very, very safe.''
The Kavanagh College pupil said he was able to queue all day because of a break in his exam period, and tried but mostly failed to study in the line.
He was relying on one energy drink and one coffee to stay awake.
''I think being around other people really brings you up.
''I'll have energy until I get home and then I'll just crash.''
Beth, a Columba College pupil, said they spent the day playing cards and making new friends.
''I've just been hanging out with the people in the line and we've all been having a really good time together.''
They only left from the queue to get food and red roses she hoped to give to the performer on her 21st birthday yesterday.
''I think it's just so cool. She's from our small country in the middle of nowhere, and it makes us feel like we can succeed too.''
Logan Park High School pupil Sofia Till, 15, said Lorde's Dunedin show in 2014 was her first concert.
''It will be really cool to see how she has grown as a performer, see how much she has changed.''
Her passion for the singer was so great, she found it hard to put into words.
''I think it's ... just ... she's like ... she's relatable.
''She grows with us.
''Her music is about stuff we can relate to.''
