Note that there are 3 world enchantments in the cube: Koskun falls, Serra Aviary and Mystic Decree.
World enchantment are an old supertype subjected to the world rule which basically states that previous world enchantments are sacrificed whenever a new one enters the battlefield (check oracle for the newest ruling).

A really tough combo is Island Sanctuary + Mystic Decree, a Reef pirates helps also.

Marjhan: There are few tricks in blue (blue being blue) to wake up (Twiddle, Chain Stasis) the monster as well as a backdoor for her to swim in for the kill Jinx

Joven's tools: There a few tricky defenders such as Cemetery gate being tough and Dark Maze as well as the kelps of Wall of Kelp being many.

Renewal: There a few tough enchantments such as Cursed Land and Orcish mine which renewal effectively get rid of.

Leeches: counters Pit Scorpion and Marsh Viper, naturally

Baron Sengir; there are really only one creature Baron will regenerate Irini Sengir, more vampires is frankly making the archtype too strong