Well, I fell for it, I was really short of yellow heroes and went for a Vivica or Joon at the Elemental.
Did the 10x summon, and I DID get Aegir.
Bad news is that I´m not happy at all, because:
Aegir is sub par as a HOTM (maybe even as a 5 star hero)
My pull gave nothing more than multiple Gan Jus, Banes and Dawas, and 2 Wu Kongs (not bad at all, but not that hard to get in TC13 or 20).
Event WAS ANNOUNCED one day after the summon.
Good news is that my judgment has improved, and I will never do that again (hopefully )