It gains vigilance, trample, lifelink, indestructible, and haste until end of turn
While this one-sided board wipe effect is already potent in its own right, Toxrill creates a 1/1 slug token whenever a creature with a slime counter on it dies, even allowing slugs to be sacrificed and converted into card draw
It a minor part of a card that's way more focused on cheating deep sea leviathans into play
No two play the same and choosing the one that best fits your playstyle and accomplishes your goals is the most important step to fun in Commander
This is information from a Carddass News The Bandai carddass part 1 is announced in a carddass news paper in September, 1996

Animal Attendant Armored Scrapgorger Devoted Druid Drover of the Mighty Druid of the Anima Druid of the Cowl Elfhame Druid Fire Sprites Frog Butler Gemhide Sliver Golden Hind Great Forest Druid Hardbristle Bandit Harvester Druid Heart Warden Hidden Herbalists Humble Naturalist Ilysian Caryatid Intrepid Stablemaster Leaf Gilder Manaweft Sliver Naga Vitalist Nest Invader Nightshade Dryad Nomadic Elf Orochi Sustainer Overgrown Battlement Overgrown Zealot Paradise Druid Petalmane Baku Poison Dart Frog Priest of Titania Prosperous Innkeeper Quirion Elves Quirion Explorer Quirion Sentinel Reclusive Taxidermist Rootrider Faun Satyr Hedonist Scaled Nurturer Scorned Villager Servant of the Conduit Skyshroud Elf Sylvok Explorer Three Tree Rootweaver Torgal, A Fine Hound Ulvenwald Captive Undercover Skrull Urborg Elf Vine Trellis Wall of Roots Werebear Whisperer of the Wilds Wirewood Elf Wose Pathfinder