An average Parian object, Istayir is carbonate, and has a large mass for a moon. It is also slightly habitable, at T_G. It cannot have a central letter due to 6-day eclipsing.
Istayir has a diameter of .74 times earth, so a mass of .57 times earth. It is slightly higher than a regular silicate planet because of its heavier magnesium and calcium based carbonate compounds.
Istayir has a day that lasts around 21 hours, and a year that lasts around 39 days. Its orbit causes it to be eclipsed by Rovaria and Voricia for six days at a time, causing quite a shift in temperature. It seems to have a few asteroids in orbit around it, and there are several artificial satellites also.
Mainly heavier carbonates, Istayir is mainly magnesite and calcite carbon compounds. Compounds include gaspeite, ankerite, and huntite. It has a large core for a moon, as it makes up for about 35% of its mass. There are several forms of titanium ore. such as perovskite and rutile.
Istayir is a slightly habitable world, with an average surface temperature of around 7 degrees celcius. All that has been introduced so far is a form of Kusa, which is terraforming the CO2 into oxygen for Rovarian use.