Leviathan of Worlds End

{u}{u}{u}{u}{u}{u}{x}{t}—If you activate this ability at
the beginning of your upkeep, create {x} 5/5 Leviathan token creatures with haste and trample.
If it is played at the end of your upkeep, create {x} 3/3 Leviathan token creatures with vigilance
haste and trample.
Leviathan creature spells cost {2} less to cast.