This was a set that was sold exclusively at Toys 'R Us for an event they had in 2002. It is incredibly rare, but I was able to find and buy it on eBay, so it does show up every now and then. In my case, it was sold with another set. Hopefully you will get lucky when you click on the links below and find it.
The set is of a Quidditch tower and is made from the colors for Ravenclaw (blue and grey) and Hufflepuff (yellow and black). I think the purpose of this was for it to be a companion set to the tower found in Quidditch Practice, but this tower is a bit smaller than the tower found in the other set.
It is one of the few sets that does not include any minifigs, nor are there any creatures. It is just the tower.
Set TRU01 - Quidditch Tower
Year Released: 2002
Set Number: TRU01-1
Name of Set: Quidditch Tower (Toys-R-Us Event Exclusive)
Book Set is Based On: Harry Potter and the Chamber of Secrets
Number of Parts: 38
Minifigures: 0
Creatures: 0
Minimum Recommended Age to Build This Set: 6 years old
Photo Source: Image used with permission by BrickLink
This LEGO® set contains small pieces that could be a choke hazard and is not meant for children age three and younger. LEGO® is a trademark of the LEGO Group of companies which does not sponsor, authorize or endorse this site.