Urborg

Legendary Land

: Add .
: Target creature loses first strike or swampwalk until end of turn.

2004-10-04:
The ability can be used on a creature without First Strike or Swampwalk but has no effect.
2008-04-01:
If a creature loses first strike after first strike combat damage has been assigned, it won’t deal damage during the second combat damage step.
2009-10-01:
You choose whether the targeted creature loses first strike or swampwalk as the ability resolves. If the creature has both abilities, it will lose just one of them.
2009-10-01:
Causing a creature to lose swampwalk is useful only during the declare attackers step or earlier. Once the declare blockers step begins, it’s too late to block the creature.
2009-10-01:
Urborg’s second ability affects only the first strike ability, not the part of the double strike ability that acts like first strike.