I can't attack someone who just stole a planet becuase no attack button appears, I also can't use artifacts on him.

The planet's population needs to be under 10 to attack anyone guarding the planet.

But I can't even purge it away on mine!

is there a vortex listed on the effects tab?...there is an artifact that prevents any other artifacts being used, reckon you found one of those being used.

on him? or on the planet? are you trying to target the person directly, through the link on your news feed? what lvl are you? what lvl is he?

or are you trying to target him through the planet he's guarding? as others have said, guards aren't attackable until the planet population is down to 10

Are you Facebook friends with him?

Mine gives me no info on who it is... just:
'This planet is completely immune to enemy actions.'

ahh. sound like someone made that planet into an exotic, dyson, or rift. you're just going to have to let it sit there. or ask dan to purge it (no garuntees he will tho)

Thank you, Revis. I appreciate the response!