I actually made a similar post to this a few months ago. As-is it’s just a worse version of the speed armor. The biggest problem being is that its mechanic doesn’t provide any benefit over using a speed set in PvP or PvE except in the most niche of cases.

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I think a good remedy would be for it to provide a combat readiness boost when attacking someone other than the caster. Then suddenly it’s interesting. I’ll leave it to the balance team to figure out how much CR per attack but at least then it’s a mechanic that is different and interesting and could have fun interactions in different game modes. 

i feel like for it to work revenge and injury needs to be a single set effect but with reduced numbers or each of those should be a 3 piece set instead of 4

Keep the 10% speed bonus, ditch the speed bonus on lower health and replace it with (triggers when 20% health lost in an attack)water's origin effect without the healing and the cr push is half of the lost health from the attack.(scales from 50% to 75% based on current health).

I don't really care as Caides too tedious to farm with the restrict and speed debuff.(I don't really want to kill my battery life).

speed scale unit mostly squishy and need turn 1, and revenge set cost HP to give u benefit, most speed unit are already dead before get the benefit

its better to change it to increase attack instead of speed, 20% att and bonus 40% as health decrease, many unit can use it, or combine it between speed and att

Add bonus armor.

I would change it to:

Increase Speed by 80% when below 50% health.

anything that doesn't require a speed substat or main stat sounds good to me. 

My idea is pretty simple, it comes from the name of the set itself. With a decrease in hp, the character receives not only a bonus to spd, but also to damage. For example, for every 1% hp - 0.1% to dmg. Since this is an increase in damage (like artifacts, Portrait for example), it will be effective for DD like BBK / Kayron  / Biseria and for characters like Krau / LRK / D.Corvus / ML Baal, etc.

I wouldn't. I plan on using it on Ruele.Not all sets have universal usage. That's what makes Speed set most desired set, it's good on 99% of units.

Delete the set.