Adamantine Sealing Chains

Kushina is able to mould her special chakra into chains which can be used to restrain targets. With it, she was able to restrain the Nine-Tailed Demon Fox in Naruto Uzumaki's mind. These chains also made up Kushina's seal, completely pinning the Nine-Tails down with several spikes in her mind.

Even while she was near death, Kushina was able to use these chains in the physical realm and restrain the Nine-Tails, enabling Minato to use the Dead Demon Consuming Seal. This involved five chains emerging from her back and burrowing into the ground, after which they would emerge and criss-cross multiple times over the target, holding them down.