Mycoid Shepherd

Whenever this creature or another creature you control with power 5 or greater dies, you may gain 5 life.

Gwenna, Eyes of Gaea

{T}: Add two mana in any combination of colors. Spend this mana only to cast creature spells or activate abilities of creature sources.
Whenever you cast a creature spell with power 5 or greater, put a +1/+1 counter on Gwenna and untap it.

Monstrous Vortex

Whenever you cast a creature spell with power 5 or greater, discover X, where X is that spell's mana value. (Exile cards from the top of your library until you exile a nonland card with that mana value or less. Cast it without paying its mana cost or put it into your hand. Put the rest on the bottom in a random order.)

Mighty Emergence

Whenever a creature you control with power 5 or greater enters, you may put two +1/+1 counters on it.

Spellbreaker Behemoth

This spell can't be countered.
Creature spells you control with power 5 or greater can't be countered.

Have

Saskia the Unyielding

Vigilance, haste
As Saskia enters, choose a player.
Whenever a creature you control deals combat damage to a player, it deals that much damage to the chosen player.