What does disjunction and vorpal do?
vorpal and disjunction were added by redpower. Vorpal gives a chance to deal large amount of damage and a chance for a mob to drop its head if it dies from the attack. Disjunction not sure, i believe has something to do with endermen i think its increased dmg to endermen or increases the chance for enderpearls to drop. Have no clue what soulstealer is, sounds soul shards related.
Dysjunction is for use vs endermen. It just makes it do more damage to them, maybe silverfish also.
Soulstealer is used for Soul shards mod. It steals extra souls to charge up a soul shard instead of the 1 per kill you normally get.