Celebrate MapleStory’s 9th Anniversary!

They've updated the patch notes with the methods to obtain the chairs.

Mercury Chair: This chair can be obtained by hunting monsters within your level range during the 9th Anniversary. (Moveable only within account, Permanent.)
Venus Chair: This chair can be obtained by participating in the 9th Anniversary Attendance Event. (Moveable only within account, Permanent.)
Earth Chair: This chair can be obtained by completing all of the 9th Anniversary Event Achievements. (Moveable only within account, Permanent.)
Mars Chair: This chair can be obtained from the 9th Anniversary Coin Shop in the Event Hall by spending 80 9th Anniversary Coins. (Moveable only within account, Permanent.)
Jupiter Chair: This chair can be obtained from the 9th Anniversary Coin Shop in the Event Hall by spending 140 9th Anniversary Coins. (Moveable only within account, Permanent.)
Saturn Chair: This chair can be obtained by hunting down the following major bosses during the 9th Anniversary, or through the Gachapon from May 7 – June 10. (Permanent.)
o Zakum (normal and Chaos)
o Horntail (normal)
o Pink Bean (normal and Chaos)
o Von Leon (easy and normal)
o Cygnus
o Arkarium (easy and normal)
o Hilla (normal and hard)
o Magus (easy, normal, and hard)
o Root Abyss bosses (normal and Chaos)
o Masteria: Crimson Wood Keep PQ bosses
o Singapore: Krexel
o Ninja Castle: Kacchuu Musha, Emperor Toad
o Malaysia: Furious Targa and Furious Scarlion
Uranus Chair: This chair can be obtained through the 9th Anniversary Gift Box. (Moveable only within account, Permanent.)
Neptune Chair: This chair can be obtained by completing the Endurance Road event and opening Secret Boxes. (Moveable only within account, Permanent.)
Obtain all eight planetary chairs to receive the “Solar Savior” quest found on the left side of the game window. Complete it to receive the Sun Chair! (Moveable only within account, Permanent.)