[b]Original Ascension[/b]
Original slayer applies a number of immunity to spell effects to prevent shapechanging to anything else, prevent portrait icon: charm, display string: you feel your control slipping, gives innate ability slayer change and end slayer change, play vfx, prevent portrait icon: level drain, play sound, cast spell: unleash (custom), cast spell: berserk at various durations.

[b]By .spl[/b]
slayer 2 adds Immunity to Effects: Disintegrate and Petrification and increases the durations by 2 rounds.
slayer 3 adds immunity to Disease and Slow, and seems to reduce the chances of going beserk drastically (it also does not display the string 'you feel your control slipping')
Slayer 4 is the Ravager, adds Immunity to Haste (probably already hasted), entangle overlay, web effect, grease overlay, and wing buffet. The chances of going berserk seem to go back up (I think you can choose between ravager and slayer in convo so that's fine?), Finger of Death immunity and Domination portrait icon immunity, disable display string (should be on the others, I think?), Immunity to animations: confusion and SPMINDAT, immune to Imprisonment, +100 HP (didn't notice these on the other slayer.spl's despite all of them supposed to give 100hp bonus.).
Unleashed applies fatigue, a sleep effect, a wing buffet, magic damage (with most settings including amount set to 0), 25% casting failure (and the icon), removes the slayer change spell, gives innate ability spin822 (slayer change)

[b]by .cre[/b]
[b]Slayer 2[/b]
Effective AC: 2
HP: 150 (up from 100?)
STR 25
DEX: 18
CON: 18
INT: 16
WIS: 9
CHA: 9
Thac0: -6 (from 0?)
# attacks: 4
race: lich (wtf, vulnerable to undead spells?)
class: mist (wtf)
morale: 20
saves: 2
Resist elements & magic/fire + cold: 50
resist weapons: 15
weapon: slayerwp (possibly an error, might need to be slayerwp2)

[b]Slayer3[/b]
HP: 200
Effective AC: -4
Magic Resist: 60
Resist Weapons: 30
weapon: slaywp3

[b]Ravager[/b]
HP: 300
AC: -10
STR: 28 (bug?)
INT: 9 (inconsistent for an 'upgrade')
THAC0: -12 (HUGE jump)
# attacks: 5
saves: 2
resist magic: 75,  resist weapons: 50
weapon1: slayerWP.itm (bug?)

[b]Items[/b]
[b]SlayerWP2[/b] (unused)
Enchantment: 5

Item Ability0: 1d12 crushing/slashing + STR damage, +5 cold damage

Item Effects: Set saving throws to 2, set AC to 2, THAC0 set to 0,
Prevent icons: Charm, Stun, Level Drain, Domination,
bonus 100 HP, max HP bonus 1, 4 attacks per round, immunity to projectiles
Immunity to effects: Level drain, imprisonment, stun
Immunity to spells: Fingers of Death,  Imprisonment (prevents anim?)
Immunity to Animations: confusion/MINDSAT

[b]SlayerWP3[/b] (unused)
Enchantment: 5
Damage: 2d8 +8 cold
On-hit: 10% to lower MR by 5 for 30 seconds
Dispel: 10% power 0 level 0 (use caster level)
play vfx: none

AC: 0
max hp bonus: 200
thac0: increment 8
hp bonus: 100

[b]SlayerWP4[/b] (ravagers)
2d8 crushing/slashing +8 Cold
10% chance to lower MR by 5 for 30 seconds
10% chance to dispel at caster level
play vfx: none
wing buffet effect (knockback?) strength 20, 25%,
sleep: 25%
display portrait icon: 25% (charm)
damage: 0 (to trigger a wake up?)

AC set to -4
thac0 set to 0
max hp bonus: 200
set to .5 attack per round
magic damage resist: 50
poison resist 50
eff: slayer 4
base thaco bonus: 12 (ending at -12)

Given that the end slayer change.spl removes the unused weapon items from the PC, I believe they were either unfinished or this is a bug in their implementation.