Source: http://nintendoeverything.com/fire-emblem-heroes-receiving-new-special-maps-starting-tomorrow/
Also, found on: https://www.reddit.com/r/FireEmblemHeroes/
I'm surprised this hasn't been mentioned already, but this connects to the topic on the news post: Starting in a few hours, we'll have new special maps each week for five weeks. Each one you beat gives three orbs, and there are two difficulty levels, meaning that's 6 orbs per week for 5 weeks - 30 total!
I'm very happy to see this, since more orbs are always good, and they're not being too stingy with orb-giving events. Let's hope the trend continues and we get even more opportunities for free orbs in the future.