That's the Odin ring, you're right that it was very easy to recreate. The hard part is the Thor ring, which increases the range of the Terra Shatterer- the increase takes place in ItemTerraPick::breakOtherBlock, not in the code for the Thor Ring class. You can look at the code on github, Botania is open source.
When the ring was removed, the methods "is<god>Ring(stack)" for each ring obviously stopped returning true for an Aesir Ring ItemStack. How can I change that back?
With the Odin ring I'm fine, and I haven't tried the Loki ring yet, but the Terra Shatterer code relies on "getThorRing(player)" which relies on "isThorRing(stack)". Do I need to learn how to use ASM, and use that to change the Botania files? Or is there another way?