msem-instigator

You may cast Gateblessed Explorer from your graveyard as long as you control three or more creatures.
Whenever another creature dies, each opponent loses 1 life and you gain 1 life.

Flying
Herald of Oblivion enters the battlefield with X -1/-1 counters on it, where X is your life total.

As long as you control no other Humans, Lone Survivor gets +2/+2 and has “Noncreature spells cost {1} more to cast.”

Exile target creature. That creature's controller creates a 1/1 blue Elemental creature token with flying.

{T}: Add {C}.
{1}, {T}, Sacrifice Perilous Passage: Destroy target nonbasic land. Activate only if an opponent controls four or more lands.

Precursor Sanctum enters the battlefield tapped. When it does, look at the top three cards of your library, exile one face down, then put the rest on the bottom of your library in any order.
{T}: Add {C}.
{4}, {T}: You may play the exiled card without paying its mana cost. Activate only as a sorcery.

Create a 1/1 colorless Construct artifact creature token. If you control an artifact, create two of those tokens instead.