Twilight's Fall – a separate game. Twilight Imperium's expansions, mods and rules topics are not part of it.

Orbital Defense Grid

At the start of invasion, choose up to 1 unit you control in the active system; that unit gains PLANETARY SHIELD. When a player commits a unit to land on a planet you control, you may exhaust this card to destroy that unit.
Mirveda ProtectorateTechnology – Warfare

Warfare

At the start of invasion, choose up to 1 unit you control in the active system; that unit gains PLANETARY SHIELD.

When a player commits a unit to land on a planet you control, you may exhaust this card to destroy that unit.

Prerequisites: WarfareWarfare

Source: Discordant Stars