Arachne

Not sure if it was only for the recent G17 Arachnes or not, but it seems to have a new skill that's similar to Puppet's Snare. I didn't know what to look for at first, so this is just a basic description where I probably missed something, but here goes:

• Arachne sends strings out to the player, immobolizes for some time (~5 sec?)
• Appears to be no damage over time, just the initial "hit" damage
• After the first effect, it lets up for an instant and then causes "hit" damange+immobolization again, but this time without the Arachne-sends-strings-at-player animation. This repeats one more time.
• For the second and third immobolization effect, Arachne's free to use other skills - Lightningbolt and Summon Monster were the ones I saw

Also, though this might just be the Shadow Mission difficulty, she summoned Burgundy Spiders on me, not Black Poisonous Spiders, though their HP seemed Hardmode-tier. Arachne's HP roughly added up to around its Hardmode level, too.