Syphon Debtors

When Syphon Debtors enters the battlefield,
place a syphon counter on each permanent you control.
(At the beginning of your upkeep, remove a syphon
counter. If you can't, exile that permanant.)
Your permanents cannot have less than
one syphon counter.
When Syphon Debtors leaves the battlefield,
remove all syphon counters from permanents
you control.