If you want to farm Silver Raid tokens really fast, then I can recommend you to exp on Oramond Factory Raids. You have raid in every 45 minutes, and from every raid you can loot at least 2 Silver Raid Tokens. This would be the fastest way to gather Silver Raid Tokens. You have there 3 types of raids:
- West Raid - Wild Life with Blood Beast, Drillworm, Wyrm, Elder Wyrm, Devourer, Glooth Anemone, Behemoth.
- South Raid- Mechanical Creatures with Worker Golem, Glooth Golem, War Golem, Rustheap Golem, High Voltage Elemental,
- East Raid - Minotaurs with Worm Priestess, Minotaur Invader,Minotaur Amazon, Execowtioner, Moohtant
About random raids, I think every raid has another chance to drop -. In my opinion the biggest drop rate is on
- A massive orc force is gathering at the gates of Zzaion.
- An orcish horde, ready for murder and plunder, is amassing to begin its travel through the steppes of Zao. Beware!
- The dragons of the Dragonblaze Mountains have descended to Zao to protect the lizardkin!
- Hungry lions scout the western Darashian desert. Travellers beware!
Sources: TibiaFandom, Tibiopedia