Loki, Scam Queen

Creatures with scam counters on them base
power and toughness 1/1 and have no abilities.
{u}{b}{r}, {t}: Gain control of a creature with a
scam counter on it, then remove the counter.
Whenever a creature enters the battlefield under
an opponent's control, you may put a scam
counter on that creature unless that creature
control pays 5 life, discards two cards, or
pays {3}.