Thanks, Sparky! Actually, at the bottom of that entry, there's a cite to page 42 of the Eberron Campaign Guide, actually I think it says "campaign setting" but it means Campaign Guide. Anyway, page 43 of the Eberron Campaign Guide has the entry for Magebred Destrier that is identical to what you posted. There is also a price chart for mounts in the ECG, and a Magebred Destrier costs 1,000 gp! Guess it's a good thing that your characters started with as much mundane equipment of whatever kind desired.
I will point out this discrepancy: in the stat block in ECG, it says the Magebred Destrier has a speed of 8, but in the "Mounts" table on the facing page, it shows the Magebred Destrier having a speed of 10, traveling 50 miles per day, and the load information is as follows -- Normal: 275 lbs., Heavy: 550 lbs., Push/Drag: 1,375 lbs. I suppose with Walking Dad just itching to get into a mounted combat, the speed discrepancy will probably come up in play sooner rather than later, and my feeling is to credit the stat block for the Magebred Destrier over the "Mounts" table, so that would make the beasts speed 8. The entry that you attached to the last post also says Speed 8, so this is not a problem at all.
The entry for Magebred Destrier says: "House Vadalis magically enhances natural creatures to breed superior versions. A magebred destrier is a superior steed valued for its endurance, intelligence, and speed." Now, I have some small issues with this description, this NOT being an Eberron game and all. But I really have no problem with the ones who came up with this breed being known as House Vadalis. (In fact, they are probably also known for their special Vidalis Onions, Vidalis Hair Tonic, or something....) There may even be a few other 'houses' here and there, but there are no Dragonmarks, no Lightning Rail, no flying ships, and elves do not have a morbid fascination with undeath and undying. So don't even be asking.