From Lineage 2 Encyclopaedia

Properties

Decrease Speed
Decreases the enemy's Speed by 20% for 1 minute.
Class	Spellhowler
Type	debuff
Attribute	-
Recast time	2 s
Cast time	4 s
Cast range	600
Classes with same skill	Wizard, Sorcerer, Necromancer, Warlock, Dark Wizard, Spellhowler, Phantom Summoner, Archmage, Soultaker, Arcana Lord, Storm Screamer, Spectral Master

Skill Upgrade

Lvl. to Learn	Skill Lvl.	Description	MP Consume	HP Consume	SP
35	1	Decreases the enemy's Speed by 20% for 1 minute.	30	0	11
40	2	Decreases the enemy's Speed by 30% for 1 minute.	35	0	30
44	3	Decreases the enemy's Speed by 30% for 1 minute.	39	0	37
48	4	Decreases the enemy's Speed by 30% for 1 minute.	44	0	67
52	5	Decreases the enemy's Speed by 30% for 1 minute.	48	0	96
56	6	Decreases the enemy's Speed by 30% for 1 minute.	52	0	105
58	7	Decreases the enemy's Speed by 30% for 1 minute.	54	0	121
60	8	Decreases the enemy's Speed by 30% for 1 minute.	55	0	151
62	9	Decreases the enemy's Speed by 30% for 1 minute.	58	0	200
64	10	Decreases the enemy's Speed by 30% for 1 minute.	60	0	210
66	11	Decreases the enemy's Speed by 30% for 1 minute.	62	0	310
68	12	Decreases the enemy's Speed by 30% for 1 minute.	64	0	478
70	13	Decreases the enemy's Speed by 30% for 1 minute.	65	0	711
72	14	Decreases the enemy's Speed by 30% for 1 minute.	67	0	748
74	15	Decreases the enemy's Speed by 30% for 1 minute.	69	0	1000