Tombstone Stairwell
World Enchantment
Cumulative upkeep 
At the beginning of each upkeep, if this enchantment is on the battlefield, each player creates a 2/2 black Zombie creature token with [[ keyword: "haste" ]] named Tombspawn for each creature card in their graveyard.
At the beginning of each end step and when this enchantment leaves the battlefield, destroy all tokens created with this enchantment. They can't be regenerated.
Dom!
Mirage (MIR)
• #149Rulings
This has the supertype world. When a world permanent enters, any world permanents that were already on the battlefield are put into their owners' graveyards. This is a state-based action called the "world rule." The new world permanent stays on the battlefield. If two world permanents enter at the same time, they're both put into their owners' graveyards.
(wotc • 2008-10-01)
You control the triggered ability, but each player controls the token creature they put onto the battlefield due to the ability's effect.
(wotc • 2004-10-04)
Both the cumulative upkeep and the triggered ability trigger at the beginning of upkeep, so you can choose what order they resolve.
(wotc • 2004-10-04)
Does not put the Zombies onto the battlefield if this card is not still on the battlefield when its ability resolves.
(wotc • 2004-10-04)
All the tokens are put onto the battlefield simultaneously.
(wotc • 2004-10-04)
If something changes the names of the tokens, then the "at end of turn" ability will still destroy them.
(wotc • 2004-10-04)
Rulings
This has the supertype world. When a world permanent enters, any world permanents that were already on the battlefield are put into their owners' graveyards. This is a state-based action called the "world rule." The new world permanent stays on the battlefield. If two world permanents enter at the same time, they're both put into their owners' graveyards.
(wotc • 2008-10-01)
You control the triggered ability, but each player controls the token creature they put onto the battlefield due to the ability's effect.
(wotc • 2004-10-04)
Both the cumulative upkeep and the triggered ability trigger at the beginning of upkeep, so you can choose what order they resolve.
(wotc • 2004-10-04)
Does not put the Zombies onto the battlefield if this card is not still on the battlefield when its ability resolves.
(wotc • 2004-10-04)
All the tokens are put onto the battlefield simultaneously.
(wotc • 2004-10-04)
If something changes the names of the tokens, then the "at end of turn" ability will still destroy them.
(wotc • 2004-10-04)