Sasscade Yo-Yo is a post Moon-Lord Yo-yo.
In order to obtain it you need to bring all the materials written in Research Note #1 along with the Note itself to the Explorer. A special dialogue option will appear.
So, you need to bring :
Shoots Homing Nebula Blazes to nearby enemies.
Blazes destroy enemies with less than 10k HP and inflicts heavy damaging debuff.
Gives effects of Yo-yo Bag while placed in inventory or being held.
Can be upgraded into True Sasscade Yo-Yo.