okay I know there is tons of Trinty Blood fans here.
I am a member of a big trinity blood fan club website and I get tons of info and stuff like that.
here is some info:
The entire Trinity Blood sereis is actually a novel, then it came out as a manga then the anime apeared. But sadly when the aniem series was announce, the creator of the novel passed away, so the series is in honor of the creator.
Terrans: term for humans
Methuselah also known as Vampires
Teams: (or groups the chracters are in) AX AGENCY (Vatican Foreign Affairs) These are the good guys
VaticanInquisitionROSENCREUTZ evil villain group
Character List (to episode 6) (don't want to overwhem you guys with so many characters)

(Peter) Abel Nightroad (Nightlord)
Codename: Crusnik
Speicies: Nanomachine Crusnik 02
Team: AX AGENCY
First appearence: ep 1

Pope Alessandro XVIII
Human
Team: Vatican
fisrt apperance: ep 1

Tres Iqus (Real name: HC-IIIX; Code name: Gunslinger)
Android
Team: AX AGENCY
First appearance: Ep 1

Kate Scott (Code name: Iron Maiden)
Human
Team: AX AGENCY
first apperance: ep 1

Cardinal Caterina Sforza (The Duchess of Milan; Head of the AX)
Human
TEam: Vatican, AX AGENCY
First Apperance: ep 1

Cardinal Francesco Di Medici (The Duke of Florence; Head of the Inquisition)
Human
Team: , Vatican, Inquisition
First Apperance: ep 1

William Walter Wordsworth (Code name: Professor)
Human
Team: AX AGENCY
First Appearance: Ep 2

Esther Blanchett (AKA "The Lady-Saint of István")
Human
Team: AX AGENCY
fisrt apperance: ep 3
Age: 15

Dietrich von Lohengrin (Code name: Marionettenspieler - "Puppet Master")
Human
Team: ROSENCREUTZ
First appearance: Ep 3

Václav Havel (Code name: Know Faith / No Face)
Human
Team: AX AGENCY
First Apperacne: ep5

Noélle Bor (Code name: Mistress)
Human
Team: AX AGENCY
first apperacne: ep 5

Hugue de Watteu (Code name: Sword Dancer)
Human
Team: AX AGENCY
First apeerance: ep 6