Spinneret and Spiderling are one Spider under the game rules
The likes of Magic and Pokemon (arguably two of the best card games ever made) have had that corner sewn up for decades, so finding space between them is, to put it generously, difficult
however, Wizards figured out that the ability to consistently destroy all lands in play on turn four might be a little too powerful
Whats incredibly surprising is that, back then, Captain Hook, Forceful Duelist was at the bottom of the list overall, so its quite a turnaround to see it at the very top of the list, even after numerous sets of the main game are out in the wild
Its also a way for players to control the board directly
All you need is a way to discard Summon: Knights of Round, and Terra can resurrect it just fine