Illidan Stormrage

Designation: Tempo Play

Replace with: Violet Teacher or Imp Master

Reasoning: While it doesn’t trigger off playing other minions, the Violet Teacher is an adequate little minion generator, focused on the playing of additional spells. Alternatively, the Imp Master would be more suited as a placeholder in a more minion-heavy deck design.

Sylvanas Windrunner

Designation: Removal Effect

Replace with: Sunwalker

Reasoning: Sunwalker might not feel like a minion that is meant for the removal role, but she can force an opponent into altering their attacking strategy. While he does not mind control an opposing minion upon death, he will at least put up a significant hurdle against a large number of smaller minions.

The Beast

Designation: Tempo Play

Replace with: Core Hound

Reasoning: Nine attack beast. It costs a crystal more, and has two less health, but without the downside of being forced into finding a way to silence your own deathrattle text.

The Black Knight

Designation: Removal Effect

Replace with: Spellbreaker or Stampeding Kodo

Reasoning: The Spellbreaker will give you just the break you need to get past a high taunt creature for a the final points of damage. If instead you are just looking for a placeholder that can squish an opponents critter, while providing a minion for later, Kodo is your man, err, beast.

Baron Geddon

Designation: Removal Effect

Replace with: Ravenholdt Assassin or Abomination

Reasoning: Seven crystal cost, check. Seven attack level, check. Five Health, check. Deals two damage to all other characters, nope, sorry. The Stealth will help this minion get some damage in, but it will do little to clear a board of minions. For that, we look to the Abomination, as long as he isn’t silenced prior to his timely demise.

Gruul

Designation: Finisher

Replace with: Boulderfist Ogre

Reasoning: See Boulderfist Ogre Section below.

Ragnaros the Firelord

Designation: Finisher

Replace with: Boulderfist Ogre

Reasoning: See Boulderfist Ogre Section below.

Alexstrasza

Designation: Unique

Replace with: Nightblade or Priestess of Elune

Reasoning: Alexstraza does one of two things, resets your opponent’s Health to 15 (dealing damage of X, where X is their current Health minus 15.) or resetting your own Health to 15 (healing X, where X is 15 minus your current health.) So the obvious placeholder is either the mid-range creature that deal direct damage to your opponent, or the one that heals yourself.