Demons hold on forsuccess in the Shield.
Throughout the first half, Cardiff were well on top and they gained the advantage after only five minutes when a deft pass from Mark Bow, saw Gareth Jones score after a typically mazy run from the half-back.
Demons extended their lead when Jones, Neil Thomas and Jamie Iles combined for an 80-metre run and after the ball ran across the face of the posts, Idris Evans picked up to ground in the corner.
It was 16-0 after 19 minutes as Jones broke through to set up Thomas while Bow's hard-fought try five minutes from half-time put the favourites 22-0 up at the interval.
The second half was a far more tense affair as Thorne desperately tried to overcome their large deficit.
But Cardiff extended their lead in the 51st minute as Graham Hughes powered over in the corner.
Following a 10-minute delay due to Marauders' Craig Linsdell suffering an ankle injury, Thorne finally got on the scoreboard.
Following an excellent interchange of passes from Nathan Hazlewood and Hookway, Shaun Carvell grounded in the corner.
Lifted by this, they scored their second from the kick-off after Mark Roach was allowed to run 60 metres to set up Carvell for his second.
Pete Moore's drop goal extended Cardiff's lead in the 60th minute,
but Marauders' Carvell completed his hat-trick with 15 minutes to go. Kevin Lake missed the crucial kick from in front of the posts.
Carvell raced in for his fourth with just six minutes left on the clock and could have had a fifth with a minute to go, but dropped the ball as he was tackled under the sticks by Moore.
Jones wrapped things up for the Demons with a last-minute penalty to complete victory for the Welshmen.
Cardiff Demons: J Iles, I Evans, R Thomas, N Thomas, A Bradshaw, G Jones, P Moore, G Hughes, M Bow, A Loxton, M Dando, D Roberson, J Byers. Subs (all used): A Jones, P Howell, T Young, K Blake.
Tries: G Jones, Evans, Thomas, Bow, Hughes.
Goals: G Jones (4).