As for not recognizing Daran when introduced by her neighbour, this could be explained either by Marelle trying to keep her true identity secret, or by Daran's unusual temporal nature affecting even her own mother's memory and making her forget about her entirely.
WMG / Flaky Pastry
The Neighbor is the Doctor, and Daran and Leslie are Susan's parents.Somehow, in the future, the Doctor and Susan get stuck in a far corner of the universe where Earth exists.
Marelle is Daran's motherDaran stated that her mother came from an alternate future to stop an eldritch abomination that eradicated all life save a dozen or so powerful beings and then gave birth to her in this past where the abomination has been contained (so far). Marelle makes sense as a candidate for being her mother from the alternate timeline, as being immortal would have shielded her from the life-ending awakening of the cosmic horror that destroyed an entire timeline, as well as giving her the time needed to learn every piece of knowledge there is in order to form a plan to stop it from ever coming back in a different timeline.
The Elfgates were created by the ancient GoblinsAfter all the Goblins were a highly advanced civilization back when the Elves were still technically cavemen and the Elfgates are old enough that the Elfgates have no idea who created them.