“Ye Who Enter Here” is episode nine of season two of Marvel’s Agents of S.H.I.E.L.D.
In the previous episode, “The Things We Bury”, Coulson’s team had managed to discover the location of the alien city that the writings Coulson, and others, were doing related to. They are now planning to head there to destroy the weapon that’s believed to be in the city before HYDRA gets its hands on it. HYDRA, of course, is not planning to destroy it.
Raina (I thought Skye’s father had killed her; must have got that wrong) is being pursued by HYDRA in Vancouver. Coulson decides to split the teams in two; his team heads to San Juan, Puerto Rico, off the coast of which the city is buried, and May’s heads to Vancouver to get Raina.
Raina mentions some blue angels – presumably the aliens whose blood was used to help Coulson. She calls them the Kree (guess it wasn’t an ice giant). I’ve come across a reference to the Kree before; not very nice aliens from what I recall. Which doesn’t bode well.