Plants/Fishing/Stones

Sola Toroid 
 Temple of Profit 
 Drops from enemies around/inside the Temple of Profit. Has a 20% chance to drop from  Kyta Raknoids .
 
 Go inside the target area. Try to get one of the enemies to put down a  Reinforcement Beacon . Wait until the beacon hits  Alert Level 4 . From this point, unlimited enemies will spawn. They will increase in level very quickly, but will eventually hit a level cap that is based on the bounty tier, and stop increasing further. 
 
 
 
 
 Vega Toroid 
 Spaceport 
 Drops from enemies around/inside the Spaceport. Has a 1% chance to drop from Mite Raknoids .
 
 A large number of Mite Raknoids will spawn during the first stage of Exploiter Orb whenever she moves across the battlefield 
 
 
 
 
 Calda Toroid 
 Enrichment Labs 
 Drops from enemies around/inside the Enrichment Labs. Has a 20% chance to drop from  Scyto Raknoid .
 
 Doing all of a Profit Taker Phase 2 bounty but not turning it in will endlessly spawn Corpus dropships. You don't even need to let the beacons hit Alert Level 4 since the drop ships will bring plenty of enemies. 
 
 
 
 
 Crisma Toroid 
 Profit-Taker Orb 
 Drops from the  Profit-Taker Orb  upon defeat during Phase 4  Heist . 
 
 
 Lazulite Toroid 
 Exploiter Orb 
 Drops from the  Exploiter Orb upon defeat.