Ultimate Completeness: A true 63/63 set means no cards are missing, saving you countless hours hunting for individual cards
"Riders" include cards like: These cards tend to be Knights that get buffs from the presence of another Dinosaur you control on the battlefield
It requires some deckbuilding foresight since it needs both artifact creatures to sacrifice and noncreature artifacts to tutor for, but thats a deckbuilding requirement well worth building around when the card can turn your measly little Thopter token into a Bolas's Citadel or Portal to Phyrexia

Gallery and List of Toxic Cards Creatures With Toxic Annex Sentry Basilica Shepherd Bilious Skulldweller Blightbelly Rat Bloated Contaminator Bloodroot Apothecary Branchblight Stalker Contaminant Grafter Crawling Chorus Duelist of Deep Faith Dune Mover Flensing Raptor Glissa's Retriever Ichorspit Basilisk Indoctrination Attendant Ixhel, Scion of Atraxa Jawbone Duelist Karumonix, the Rat King Mite Overseer Monument to Perfection Myr Convert Necrogen Rotpriest Nimraiser Paladin Paladin of Predation Pestilent Syphoner Plague Nurse Porcelain Zealot Ribskiff Sheoldred's Headcleaver Skrelv, Defector Mite Slaughter Singer Stinging Hivemaster Tainted Observer Tyrranax Atrocity Tyrranax Rex Unctus's Retrofitter Venerated Rotpriest Venomous Brutalizer Venser, Corpse Puppet Vishgraz, the Doomhive Voidwing Hybrid Cards that Grant Toxic Toxic Matters Cards These cards don't necessarily have or grant toxic, but mention the mechanic by name in one way or another
Greens most explosive mana engine