From Lineage 2 Encyclopaedia

Properties

Poisonous Cloud
Creates a poison cloud around the enemy, causing loss of 24 HP per second for 30 seconds.
Class	Spellhowler
Type	debuff
Attribute	-
Recast time	5 s
Cast time	4 s
Cast range	500
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
25	1	Creates a poison cloud around the enemy, causing loss of 24 HP per second for 30 seconds.	34	0	6
35	2	Creates a poison cloud around the enemy, causing loss of 32 HP per second for 30 seconds.	45	0	11
48	3	Creates a poison cloud around the enemy, causing loss of 41 HP per second for 30 seconds.	65	0	67
56	4	Creates a poison cloud around the enemy, causing loss of 50 HP per second for 30 seconds.	77	0	105
64	5	Creates a poison cloud around the enemy, causing loss of 58 HP per second for 30 seconds.	89	0	210
74	6	Creates a poison cloud around the enemy, causing loss of 63 HP per second for 30 seconds.	103	0	1000