1 Herald of Khorne
Two activations if he strikes and if he is within a range of a blood letter unit also that bloodletter unit gets re-rolls to hit of 1s.

1 Bloodsecrator
When he useis his abilty all Khorne keyword units gain 1+ attack to all weapons and make everyone immune to battleshock that are keyword Khorne.

1 Bloodstoker
When he targets a friendly Khorne unit they get +3" run/charge and re-roll to wounds of 1s

Unit of 20 Bloodletters or more
Due to having 20+ bloodletters they have +1 to there hit results of there weapons

So that means these bloodletters can reroll hits and wounds of 1s charge a possible 15" and get 2 attacks each wile hitting on 3+ that if rolling a 6 cause's a mortal wound so if about 10 of them got in close combat that means they get 20 attacks your guarantee to get at least some mortal wounds in that attack