Spawning Pool

This land enters tapped.
{T}: Add {B}.
{1}{B}: This land becomes a 1/1 black Skeleton creature with "{B}: Regenerate this creature" until end of turn. It's still a land. (If it regenerates, the next time it would be destroyed this turn, instead tap it, remove it from combat, and heal all damage on it.)

Tenth Edition

Spawning Pool comes into play tapped.
{T}: Add {B} to your mana pool.
{1}{B}: Spawning Pool becomes a 1/1 black Skeleton creature with "{B}: Regenerate this creature" until end of turn. It's still a land.

World Championship Decks 1999

Urza's Legacy

Spawning Pool comes into play tapped.
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T: Add one black mana to your mana pool.
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B Spawning Pool becomes a 1/1 black creature with "oo
B Regenerate this creature" until end of turn. This creature still counts as a land.

A noncreature permanent that turns into a creature can attack, and its {T} abilities can be activated, only if its controller has continuously controlled that permanent since the beginning of their most recent turn. It doesn't matter how long the permanent has been a creature.

Activating the ability that turns it into a creature while it's already a creature will override any effects that set its power and/or toughness to a specific number. However, any effect that raises or lowers power and/or toughness (such as the effect created by Giant Growth, Glorious Anthem, or a +1/+1 counter) will continue to apply.