If I were you, I’d lower the damage to 310-370, so slightly higher than QoT, but with a higher MP cost. I’d also remove the Spd debuff and add +2 Att and +2 Dex. I’d also reduce the Slow time to 2.5 seconds.
The sprite is okay, by the way. It’s not my favorite, but if it were shaded to be somewhat like the color of an Att ring’s gem, I think it’d look better.
Overall, not a bad concept, but it’s unbalanced. 5/10.