So I found it, here is the Imgur link with screen shots of stats and stuff.
New Trinket: Misplaced Promissory Note.
Tested on Divine/Grey/Ancient/Blizzbreaker set.
It seems like the more defenses you have, the more effective this trinket is.
We used T3 Shufflebot Tackle attacks with Divine/Grey/Ancient/Bizzbreaker set and saw a damage decrease per hit when my health got lower.
https://wiki.spiralknights.com/Shufflebot (Note that it only does Normal damage)
We then tested it on Knocker Reaction attacks with Dread/Grey sets and it had no effect.
https://wiki.spiralknights.com/Knocker (Note that it only does elemental damage).
Then we tested it on Zombie Swipe attacks with Dragon/Grey/Dread sets and it also had no effect.
https://wiki.spiralknights.com/Zombie (Note that it only does shadow + normal damage).
Thanks to Instant-Noodles for helping me with number crunching and Zethalan for standing pretty when we met up.
*sees a trinket that actually decrease damage taken, something people have been asking for years that can make a tanky build viable*
Finally GH is actually listening, too bad this does take up a trinket spot that may be better suited for a hear pendant.
Damage decrease only works on normal-based attacks, not mixed.
So in another word it is almost useless in T3, *Insert facepalm gifs here*
Perhaps it only effects its own buff or just normal defense in general. Could someone try to see how well it does when you have dragon scale set or ancient on?
You take less damage the lower your health?
Went into training hall and used the Shufflebots to take normal damage with a divine set on. First hits at full hp were 5% damage per hit, at round 50% hp they were doing 2-3% per hit.