The last poem/riddle was about Zoe Heriot!
The people who guessed correctly are LilactheDryad and Anjion.
The next person I'm doing was chosen by LilactheDryad!
I was an imprint of an inter-dimensional being,
which existed in many realities.
I always ended up as same the thing,
sharing the same basic attributes,
although the Intelligences originated in various ways,
including an immortal soul,
and various Great Old Ones.
I began life as James Lethbridge-Stewart
and ended life a millennia later as Mahasamatman.
In another reality I was originally from the universe before the Doctor's,
the being known as Yog-Sothoth.
My brethren and I survived the end of our universe by passing through a parallel universe,
that ended one second after ours.
We shifted again allowing us to enter the current universe shortly after it began expanding.
In a third reality I was an Great Old One.
Like the other Great Old Ones,
I may have lost my body when I ran from the Fendahl.
The People I have done:
The Doctor
Rory
River Song
Cassandra
Rose Tyler
Clara Oswald
Strax
Sarah-Jane Smith
The T.A.R.D.I.S
Missy
Daleks
Donna Noble
Vastra
Weeping Angels
Martha Jones
Slitheen
Tom Milligan
Creature from Midnight
Captain Jack Harkness
Zoe Heriot