Head to Ranni's Rise, leave it and start travelling ... It should say "Seluvis's Puppet. Do not touch". 5. Return to Seluvis and talk with him about the hidden chamber. Then you'll get the option ...

Namely that doing Blaidd's questline also requires you to complete both Ranni's quest, and the Elden Ring Sorceress Sellen questline. However, the latter of these isn't too drastic, and they're ...