"Old Stickfingers" can send a number of creature cards to the graveyard, then gain power and toughness based on how many creatures are in the graveyard
Every card that exists on Arena and is legal in Pioneer is legal in Explorer, and nothing more than that
Grixis Dragons - Magic 2019 Standard | ASTRALPLANE, (5-0) MTGO Creatures (20) 2 Demanding Dragon 2 Pia Nalaar 4 Glorybringer 4 Goblin Chainwhirler 4 Nicol Bolas, the Ravager 4 Scrapheap Scrounger Planeswalkers (5) 2 Sarkhan, Fireblood 3 Chandra, Torch of Defiance Instants (8) 2 Magma Spray 2 Unlicensed Disintegration 4 Abrade Artifacts (2) 2 Heart of Kiran Lands (25) 6 Mountain 1 Scavenger Grounds 2 Aether Hub 4 Canyon Slough 4 Dragonskull Summit 4 Spirebluff Canal 4 Sulfur Falls Sideboard (15) 1 Angrath, the Flame-Chained 1 Magma Spray 1 Hour of Glory 1 Spit Flame 2 Chandra's Defeat 3 Negate 1 Banefire 2 Doomfall 3 Duress When Sarkhan, Fireblood and Chandra, Torch of Defiance come together in the same deck, you have the possibility of some explosive turns
Just be careful, though, as smart players will force the Buckaroo! The new Kaldheim board wipe, Doomskar, is another card that can come down for three mana when foretold, which helps massively with rebuilding the board afterwards
You can name a specific card that creates those tokens, but that's as far as this needle goes
