Board Thread:Lore Discussion/@comment-24098614-20150903093108/@comment-1470368-20150918124206

The Blades are known to the Greybeards as those who've used the Dragonborn, not the other way around. They claim to serve the Dragonborn, but in reality the Blades manipulate the ultimate Dragon-slayer.

There is no substantial reward for serving the Blades. You can easily get the Dragon Infusion Perk from the special potion made by Esbern BEFORE being "forced" to kill Paarthurnax just to gain access to their services.

Screw them, I say. Their usefulness is done in the moment that you gain the permanent Dragon Infusion Perk.