Crimson charm

Crimson charms are used in Summoning to summon certain creatures. The amount of experience gained from each charm use varies between 83.2 and 1015.2 depending on the pouch made, making crimson charms the second most powerful charm after blue charms. Crimson beats out blue in one respect — creating a Talon beast pouch using a Crimson charm gives 1015.2 xp, the highest of any pouch.

Familiars
The following familiars require a Crimson charm to make their pouch:

Monster (Percent Crimson Charm Drop)

 * Aberrant spectres (7-8%)
 * Abyssal demons (40-41%)
 * Ankous (5-9%)
 * Armoured zombies (3-4%)
 * Basilisks (5-6%)
 * Bats (1-2%)
 * Big Wolf
 * Black bears (0-2%)
 * Black demons (48-50%)
 * Black Knights (2-3%)
 * Black unicorns(1%)
 * Bloodvelds (rare)
 * Bloodworms
 * Blue dragons
 * Bork (100% drop of 7)
 * Cave crawler
 * Chaos Dwarf
 * Cockatrice
 * Cockroach soldiers (very common)
 * Cockroach worker
 * Cow (fairly rare)
 * Dagannoth
 * Dire Wolves
 * Druids
 * Dust Devils (common)
 * Earth Warriors
 * Fire Giants
 * Fire Elementals
 * Flesh Crawlers
 * Giant rock crabs- (3 at a time, common)
 * Ghouls
 * Goblins
 * Greater demons *common)
 * Green dragons
 * Grizzly bears
 * Guards
 * Hellhounds
 * Hill Giants
 * Icefiend
 * Ice giants
 * Ice Warriors (uncommon)
 * Infernal Mage
 * Iron Dragons- (2 at a time)
 * Jellies
 * Jogres
 * Kalphites
 * Khazard Troopers
 * King Black Dragon- (4 at a time)
 * Kurasks
 * Lesser demons
 * Locust riders
 * Mithril Dragons- (4 at a time)
 * Moss giants
 * Monkeys (rare)
 * Nechryaels (common)
 * Ogres (uncommon)
 * Pyrefiends (uncommon)
 * Rock Crabs
 * Rock Lobster - (2 at a time, common)
 * Shadow Warriors (common)
 * Scorpions
 * Skeletal Wyverns (common)
 * Skogres
 * Steel Dragons- (3 at a time)
 * Suqahs
 * Tormented Demon- (3 at a time, fairly common)
 * Tormented Wraith (common)
 * Troll Generals
 * Turoths
 * Wall Beasts
 * Waterfiends (extremely common, one of best droppers)
 * Wizards
 * Wolves
 * Zogres (uncommon)

Other sources
Thieving
 * Dorgesh-Kaan Average Chest
 * Dorgesh-Kaan Rich Chest

Other Methods
 * Soul Wars rewards
 * Random event gifts
 * Spirit implings (not by buying jars)