This EGO has two things going for it in Awakening: the ability to burst Tremor and the ability to inflict additional Sinking Count (and Sinking Potency at Threadspin IV).
Sinking Count by itself isn't that notable, unless you have additional Sinking Identities that can inflict both Potency and Count, as otherwise you're only dealing 1 Sinking damage to an enemy at a time, even if it has multiple Count.
This all changes when the EGO is Threadspun up to IV, as now she inflicts a significant amount of Sinking Potency to take advantage of the Sinking Count she can inflict. Ideally, you would have other Sinking Identities to keep the Sinking train going.
As mentioned earlier, this EGO can also burst Tremor, but since its primary use is to inflict tons of Sinking against multiple enemies, this additional effect is generally underutilized. It may see some use when paired with a Rodion Identity that naturally inflicts Tremor such as her Rosespanner Identity.
Its base and maximum power is pretty good too, even when not Threadspun yet, as it can reach a maximum of 28 before Threadspin III and 30 after Threadspin III, which is enough to win against most clashes in Mirror Dungeon 2 Hard. Plus, the EGO itself can deal additional damage against enemies above 50% HP, which makes it better when used early.
It's also interesting to note that, unlike the Corrosion version of this EGO, the Awakening version immediately starts off with 3 AoE slots. The Corrosion version only gets 3 AoE slots at Threadspin IV.
The Corrosion of this EGO is an enhanced version of the Sinking that Awakening inflicts, dishing out double the Sinking potency of the Awakening EGO at Threadspin IV and almost double the Sinking Count. Basically, if you're more interested in inflicting additional Sinking than just the Awakening of this EGO, Corrosion is where its at.
It also bursts Tremor which, as mentioned earlier, is not really what this EGO is primarily used for, but may be nice to have. It also has a similar effect of dealing bonus damage on enemies above 50% health.
Interestingly, its maximum power is not as good as it is in Awakening, only managing to reach 23 pre-Threadspin III while reaching 27 post-Threadspin III, making it not as good in clashes. In other words, if you're using the Corrosion version, you're more interested in the amount of Sinking it inflicts, even with less clash and damage prowess for the skill.
A passive that complements her Sinking infliction, making her great at debuffing enemies's speed and attack power. It works best after she has used her EGO and it is Threadspin IV, as Threadspin IV inflicts Sinking Potency and the Sinking Count that accompanies it is more than enough even if some of her allies without Sinking go first before she can hit her enemies with the passive.
Sinking fans rejoice, for Rime Shank is here to save the day. While Rodion herself does not have any Sinking Identities herself, her Rime Shank EGO can pick up the slack. When you wish you had more Sinking to make Spicebush Yi Sang's Sinking Deluge worth it so he can actually activate it, you turn to Rime Shank.
Rime Shank's true potential isn't unlocked until Threadspin IV, so just keep that in mind. Before that, Rime Shank inflicts a decent amount of Sinking Count but no Sinking Potency to speak of. At, Threadspin IV, this problem is fixed, and now Rime Shank is a must in stacking copious amounts of Sinking Count and Potency against enemies.
Identities like Molar Boatworks Fixer Ishmael, who can inflict tons of Sinking on her own and also benefits from enemies having lots of Sinking, and Spicebush Yi Sang, who has the special ability Sinking Deluge, that deals all of the SP damage (or Gloom damage for Abnormalities) according to the amount of Sinking an enemy has, are perfect Identities to pair with any Rodion with Rime Shank.
The biggest thing you'll probably be keeping an eye on his how to fuel it. It uses Gloom and Envy which , while her Rosespanner Identity can provide, she'll be thankful for having additional allies that can also make it much easier for her to use this EGO.
All in all, when building a Sinking team, you really want this EGO there. Rodion herself doesn't even need to be able to inflict Sinking. What's important is that Rodion is there and can maybe fuel her EGO.