Splendid Agony

Distribute two -1/-1 counters among one or two target creatures.

Hapatra, Vizier of Poisons

Whenever Hapatra, Vizier of Poisons deals combat damage to a player, you may put a -1/-1 counter on target creature.
Whenever you put one or more -1/-1 counters on a creature, create a 1/1 green Snake creature token with deathtouch.

Nest of Scarabs

Whenever you put one or more -1/-1 counters on a creature, create that many 1/1 black Insect creature tokens.

Prowling Serpopard

This spell can't be countered.
Creature spells you control can't be countered.

Festering Mummy

When Festering Mummy dies, you may put a -1/-1 counter on target creature.

Harvest Season

Search your library for up to X basic land cards, where X is the number of tapped creatures you control, put those cards onto the battlefield tapped, then shuffle.