Ethereal

Ethereal (sometimes referred as ghost form) is a type of status effect that makes the targets immune to physical damage while also disarming them. It also reduces their magic resistance, causing them to take additional magical damage. Besides being unable to attack, afflicted units can still act freely, move around, cast spells and use items.

Ethereal units cannot be directly attacked, not even with manually cast active attack modifier like. However, they still are fully affected by spells, even those which deal physical damage, blocking their damage but not preventing their other effects. For example cannot damage ethereal units, but can still stun and slow them. Ethereal state does not dispel any buffs or debuffs, but the ethereal from items will cause Naga Siren's to not affect the targeted unit.