Dark Depths enters with ten ice counters on it.

: Remove an ice counter from Dark Depths.
When Dark Depths has no ice counters on it, sacrifice it. If you do, create Marit Lage, a legendary 20/20 black Avatar creature token with
flying (This creature can't be blocked except by creatures with flying or reach.) and
indestructible (Effects that say "destroy" don't destroy that permanent. An indestructible creature can't be destroyed by damage.).