Both times, it's a representation of the Big Five, Kaiba Corp's former leaders who became trapped in Noah's virtual world
You get incredible control over your draw step, plus a lot of graveyard value
The main cards to look out for in the future would be The Fiendsmith, a cheeky Link-1 monster called Fiendsmith's Requiem, and lastly, the big boss of the pack Fiendsmith's Desirae which is a fusion monster
Unlike Fatal Push, they are just good against almost everything
Adventures in the Forgotten Realms manages to inject some decision-making by having cards literally named after classic D&D prompts like Choose Your Weapon and You Come to a River
(All dice must be stacked vertically, one on top of another.) Boomstacker gets +1/+1 for each die in its stack