What stats does Radiant Void Staff give?

Radiant Void Staff grants 75 AP and +30% AS.

What kind of item is Radiant Void Staff in TFT Set 17?

Radiant Void Staff is a Radiant item in TFT Set 17.

Damage from attacks and Abilities 30% Shred the target for the rest of combat.

radiant

Damage from attacks and Abilities 30% Shred the target for the rest of combat. This effect does not stack.

Shred: Reduce Magic Resist

Shred

Reduces the target's Magic Resist (commonly by 30%, though the amount varies by source) for a duration, or for the rest of combat with some effects.

Magic Resist

The magic-defense stat that reduces incoming AP damage. Many sustain items, the Bastion frontline trait, and "Gain X Armor and Magic Resist" effects grant or scale off it; Shred is its inverse.