Gorex, the Tombshell
Legendary Creature — Zombie Turtle
As an additional cost to cast this spell, you may exile any number of creature cards from your graveyard. This spell costs 
less to cast for each card exiled this way.
Deathtouch
Whenever Gorex attacks or dies, choose a card at random exiled with Gorex and put that card into its owner's hand.
Wisnu Tan
Commander Masters (CMM)
• #164Rulings
Gorex's first ability can't reduce its cost below {B}{B}. You can exile any number of creature cards from your graveyard, even if they won't reduce Gorex's cost any further.
(wotc • 2021-09-24)
Include any additional costs to cast Gorex before applying its own cost reduction. For example, if Gorex is your commander and an additional cost of {6} applies from the "commander tax," you may cast Gorex by exiling four creature cards from your graveyard and paying {4}{B}{B}.
(wotc • 2021-09-24)
Rulings
Gorex's first ability can't reduce its cost below {B}{B}. You can exile any number of creature cards from your graveyard, even if they won't reduce Gorex's cost any further.
(wotc • 2021-09-24)
Include any additional costs to cast Gorex before applying its own cost reduction. For example, if Gorex is your commander and an additional cost of {6} applies from the "commander tax," you may cast Gorex by exiling four creature cards from your graveyard and paying {4}{B}{B}.
(wotc • 2021-09-24)