Grimy torstol: where to get it

Source	Quantity	Chance per roll
Adamant dragon	1	1/73.33
Alchemical Hydra (Serpentine)	10–15	1/107.7, 2 rolls
Ancient chest	1–134	1/33, 2 rolls
Ancient Wyvern	1	4/132
Ancient Zygomite	1	6/118
Basilisk Knight	1	1/92.44
Basilisk Sentinel	1	1/92.44, 3 rolls
Blood Reaver (Ancient Prison)	1	1/68.27
Cerberus	6	4/130
Chest (alchemist's signet)	1	1/5.33
Colossal Hydra	3	1/320, 3 rolls
Dark Chest	10–15	25/600
Drake	1–3	1/165.3
Extra supply crate	1–3	Varies
Grimy Lizard	1	1/682.67
Grubby Chest	5	7/100
Guardian Drake	1–3	1/165.3, 3 rolls
Herbiboar	1–4	Varies
Hydra	3	1/320
Kalphite Queen (Crawling)	25	2/126
Long-tailed Wyvern	1	2/123
Manta ray	2–3	1/264
Monumental chest	20–24	1/30, 3 rolls
Opulent salvage	1	1/226.13
Phosani's Nightmare	13–26	4/100
Reward Cart	1–3	Varies
Rune dragon	1	1/84.67
Sarachnis	5–10	6/800
Scorpia	10–15	5/128
Sinister chest	1	Always
Skotizo	20	7/100
Spiritual Mage (Zaros)	1	8.875/128
Spiritual Ranger (Zaros)	1	1/68.27
Spiritual Warrior (Zaros)	1	1/68.27
Spitting Wyvern	1	2/123
Stingray	1–2	1/533.3
Taloned Wyvern	1	2/123
The Nightmare	1–16	4/100
Tormented Demon (1)	1	1/136
Torstol (plant)	1	Always