Betelgeuse

The red giant star, Betelgeuse, is Alpha Orionis.

In Poul Anderson's Technic Civilization History, Betelgeuse has forty seven planets, six bearing life. The star's total radiation is great enough that its liquid water zone includes that many planetary orbits; however, not long enough for life, let alone intelligence, to develop. Because Betelgeuse is much more massive than Sol, it has spent only a short time on the main sequence and is dying.

Human explorers found an interplanetary civilization with vague traditions, although no extant records, of ancestors arriving from elsewhere and seeding lifeless planets:

engineered microorganisms can generate a breathable atmosphere in decades;
automated processes can produce soil;
plants and animals grown from cells can then be released.

Betelgeuseans:

have hereditary rulers called Sartazes;
now have the hyperdrive;
rule a few nearby stars;
will evacuate their system when necessary;
play potential enemies, like Terra and Merseia, off against each other;
are treated as a buffer state between imperia and barbarians;
have human citizens, some in key positions;
are short, stocky, bald and blue with large yellow eyes in round blunt faces;
trade with the human colonies, Altai and Unan Besar;
thus were, indirectly, the means by which Dominic Flandry ended Merseian subversion on the former and a dictatorship on the latter.

Chereion

Originally published on Poul Anderson Appreciation, 23 May 2012.

The planet Chereion is in the Merseian Rhoidunate. Landing on it is forbidden by each new Rhoidun. Merseian warcraft protect its system to the death.

Chereion's sun is a red dwarf star, billions of years older than Sol or Zoria, with seven planets. Chereion has polar caps, barren deserts, uncultivated saline plant life, a few shrunken seas and a small scarred moon. Chereionite gravity is half terrestrial. Much atmosphere and hydrosphere have been lost. There is overwhelming age and desolation. Cities are in good repair with fusion power but little energy use and with no visible traffic or ground or satellite defenses. There are lighted towers in the middle of rock and sand wastes.

A Chereionite city is surrounded by low glittering rainbow bushes, then by lifeless desert and eroded mountains. The city, enclosed in an ellipse, comprises, at the perimeter, single-storied, slenderly colonnaded buildings. Beyond these, other buildings lift towards slim towers. There are harmonious colors but few windows and no sounds. Landscape erosion has revealed the city's azure foundations.

Streets are broad and blue. Man-sized floating ovoids with tentacles holding tools and sensors maintain the buildings. In a mosaic plaza, computer-generated holograms of extinct Chereionites walk in apparent contemplation and mind to mind communication, preventing the Merseians from realizing that only one Chereionite survives. Aycharaych, who trained high ranking Merseians in his castle at Raal, preserves recordings not only of his planet's art and literature but also of its spiritual leaders and philosophers. He says that the Chereionites were the Ancients whose ruins are found on many planets. 

Sources: 

Anderson, Poul, The Day Of Their Return, Doubleday, 1973; 
A Knight Of Ghosts And Shadows, London, 1978;  
A Circus Of Hells, London, 1978, p. 116.