Verified for patch 16.8.1

Aegis of Dusk

Every 2.5 seconds, steal 3 Magic Resist from enemies within 1 hex and deal ?% of the holder's Magic Resist as magic damage.

If Aegis of Dawn is also equipped, trigger this item's effect every 1.25 seconds instead.

Damage increases based on Stage.

Source

Artifact

Effects

Health: 400
MRStealPerTick: 3
MagicResist: 70
TickRate: 2.5
TickRateWithAegisOfDawn: 1.25

Aegis of Dusk enables

Magic Resist On the Menu

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