Since others have suggested NPC planets, bases, and others, why not missions that acts like a NPC?

The NPC missions are in a separate tab and instead of rounds and completions, they would have health points and various commands, random with random missions. You need various amounts of various artifacts in cargo to do damage. These artifacts will not be used when using various commands, there is a limit on how much you can "damage" the health of the mission. These missions will be matched with rank, some can be matched with stats, race, profession, etc. These will only have one completion. Each player has one NPC Mission slot, every 200 ranks, another slot is granted. Each mission has their own rarity, and some are boss/elite missions (not yet thought of).

Timer to Expiration:
Common NPC Missions: 8 hours
Uncommon NPC Missions: 24 hours
Rare NPC Missions: 24-48 hours
Extremely Rare NPC Missions: 36-48 hours
Elite NPC Missions: 24-48 hours
Boss NPC Missions: 36-60 hours

I already have a few thought up: (Rank 100 Examples) (Common Missions)

Attack Command NPC Missions:

Fleet Engage
There is a fleet of ships in one group that are heading your way. Take them down and your reward will be given.

Mission Health: 1500
Attack Command: 10 Energy
Artifacts Required: Spy Probe - Weapons
Max Limit Damage: 250 (5 Spy Probe - Weapons) (50 damage for each)
EXP / Attack: 20-30XP
Reward: Fleet Scraps - Trade them for Credits or scrap them for Complex Tech Parts

Planetary Collision
A planet is out of orbit and is now heading a direct course to your ship!

Mission Health: 2500
Attack Command: 10 Energy
Artifacts Required: Ancient Crystal Foci
Max Limit Damage: 500 (10 Ancient Crystal Foci [Each does 50 damage])
EXP / Attack: 20-30XP
Reward: Planet Resources - Grants 3 hours of Mining, Artifact, and Research production.

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Defend Command NPC Missions:

Supernova Outburst
A nearby star has exploded into a supernova, sending mass asteroids to your ship!

Mission Health: 10 Asteroids
Defend Command: 10 Energy
Damage of Asteroids: 50-250 (Based on defense of your ship)
EXP / Defend: 20-30XP
Reward: Defense Grid - +10% Defense for 4 hours.

Planetary Invasion
One of your planets are under attack. Go over to the planet and guard it.

Mission Health: 25 Attacks
Defend Command: 10 Energy
Damage of Attacks: 50-500 (Based on defense of your ship)
EXP / Defend: 20-30XP
Reward: Invasion Defender - Planet Artifact: Size 1, Invasion Defense: 300

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Hack Command NPC Missions:

Research Riot
A nearby research station was in flames due to a riot. Hurry and hack all the data you can find.

Mission Health: 5000 Research Points
Hack Command: 5 Energy
Artifacts Needed for Hack: Dark Pyramids
Max Amount that can be Hacked: 500 RP (5 Dark Pyramids [100 RP hacked for each one])
EXP / Hack: 10-20XP
Reward: Critical Hack Data - Increases critical hack success by 5% for 30 minutes

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Uncommon and rarer + elite/boss NPC Missions will be updated in this post. What do you think?

It's not such a bad idea, but I think that the plots of the missions are well...a little tacky. If there is a rogue planet heading you way, can't you just move out of the way? And if a supernova goes off, sending debris at you, wouldn't it be wise to jump into warp, hyperspace, or other FTL drives to escape and outrun the debris and shockwave? Other than that, I suppose it's okay.