From the Super Mario Wiki
“Please Mario... We need your help... We will...”
Eldstar is one of the seven Star Spirits in Paper Mario. As indicated by his name, he's the elder of Star Haven and seems to be the leader of the other Star Spirits. He has a large white mustache, white eyebrows, and dark green eyes.
Eldstar, along with the other Star Spirits, visits Mario after his loss to Bowser during the opening moments of Paper Mario. While Mario is unconscious, Eldstar comes to him in a dreamlike state and tells Mario that he must go to Shooting Star Summit. He then disappears, and when Mario asks the Toad about it, he tells Mario that he didn't see anyone go in or out.
When Mario arrives at Shooting Star Summit, Eldstar is waiting for him. He and the other Star Spirits tell Mario that Bowser has captured them, and that they are only talking to him through a spiritual link that will soon be extinguished. He tells Mario and Goombario that to stop Bowser and save Princess Peach, Mario must first rescue the Star Spirits.
Eldstar is guarded by the Koopa Bros. and is the first Star Spirit rescued. He grants Mario the powers of Refresh and Focus.
"Advice From The Star Spirits" Entry
Eldstar's "Advice From The Star Spirits", from the Paper Mario instruction booklet is as follows:
Eldstar's Hint: When you see a "!" mark, explore.
Mario Party 5
In Mario Party 5, Eldstar is the guide of party mode. Like in Paper Mario, he is the leader of the Star Spirits. He seems to dislike everything, saying "How awful" even if the 5 stars on the board event is triggered. He also says that it looks bad when a duel occurs even though this can be an advantage at times.
Super Smash Bros. Brawl
Names in other languages
“He's an old Star Spirit. His name is Eldstar. He reminds me of my grandpa. He's a revered person who lives in Star Haven, way up beyond the sky. Uh...a revered star, I mean. I wonder why he's here. He should be in Star Haven. And why does he look so... dim? I can see right through him.”