what is a blood knight and how do you get 1?

A Blood Knight is a Blood Elf Paladin, they go by the name of Blood Knights.

Blood Knights bend the light to their will, instead of worshiping it, like alliance paladins. BLOOD ELF PALADINS ARE STILL CALLED PALADINS- JUST LORE WISE NAMED BLOOD KNIGHTS.

NOT to be confused with Death Knights

what is a blood night and how can u get 1?

Death Knight
FD_Deathcrush- + 10, 15, 22, 44, 65, 100 weapon dmg for 10, 12, 15, 17, 19, 21 sec.
1, 1, 1, 2, 4, 6 Runecost
Instant
PD_Felcrush- The Death Knight channels powerful demonic energies for 4.85 sec to reduce the target's hit
and critical chance by 4%, 10%, 15%, 20% for 11 sec.
7, 8, 9, 10 Runecost
1 min Cooldown
AD_Bloodcrush- The Death Knight pays with 15% of his hp having 45% chance to stun the target for
2, 4, 6 ,8 ,10 sec. Awards 1 Rune.
0 Runecost
Instant
FD_Ghostcrush- The DK pays with 17%, 18%, 19%, 20% of his life to get 50% ms for 4, 5, 6, 7 sec becoming immune to magic effects.
Awards 2 Rune.
0 Runecost
8 sec cooldown

Rune Sistem
Azure Dream- The Death Knights gets +1 Rune every 5 sec.
Plague Dream- +1 Rune on runeblade critical strike.
Dark Dream- +1 Rune with 50% chance of another point spent using a Crush.
Frozen Dream- +1 Rune with every block, resist, dodge or parry.
(every Dream has 50 sec cooldown- One Active at a time)

AD, PD, FD_Final Blow- If  the target has under 10% chance reduces all damage taken by the Death Knight by 95%
and makes him immune to Snare effects. Lasts 9 sec. Can be activated when the target has over 10% hp.
5 Runecost
45 min Cooldown
AD _Blackshield- + 2%, 4%, 6%, 8%, 10% , 12% , 14%, 16% armor and ms for 1h.
2, 4, 6, 8, 10, 12, 14, 16 Runecost
Instant

LoL, Snare...