Feral Ghoul

Menace
Whenever another creature you control dies, put a +1/+1 counter on Feral Ghoul.
When Feral Ghoul dies, each opponent gets a number of rad counters equal to its power.

Altar of the Brood

Whenever another permanent enters the battlefield under your control, each opponent mills a card.

Radiation

At the beginning of your precombat main phase, if you have any rad counters, mill that many cards. For each nonland card milled this way, you lose 1 life and a rad counter.

Zellix, Sanity Flayer

Hive Mind — Whenever a player mills one or more creature cards, you create a 1/1 black Horror creature token.
{1}, {T}: Target player mills three cards.
Choose a Background (You can have a Background as a second commander.)

Mindcrank

Whenever an opponent loses life, that player mills that many cards. (Damage causes loss of life.)

The Wise Mothman

Flying
Whenever The Wise Mothman enters the battlefield or attacks, each player gets a rad counter.
Whenever one or more nonland cards are milled, put a +1/+1 counter on each of up to X target creatures, where X is the number of nonland cards milled this way.

Hedron Crab

Landfall — Whenever a land enters the battlefield under your control, target player mills three cards.

Ruin Crab

Landfall — Whenever a land enters the battlefield under your control, each opponent mills three cards. (To mill a card, a player puts the top card of their library into their graveyard.)

Grindstone

{3}, {T}: Target player mills two cards. If two cards that share a color were milled this way, repeat this process.

Eye Collector

Flying
Whenever Eye Collector deals combat damage to a player, each player mills a card.

Lord of Lineage

Flying
Other Vampire creatures you control get +2/+2.
{T}: Create a 2/2 black Vampire creature token with flying.

Bloodline Keeper

Flying
{T}: Create a 2/2 black Vampire creature token with flying.
{B}: Transform Bloodline Keeper. Activate only if you control five or more Vampires.

Bloodline Keeper // Lord of Lineage

Intruder Alarm

Creatures don't untap during their controllers' untap steps.
Whenever a creature enters the battlefield, untap all creatures.