Bjorna, Nightfall Alchemist

Arvinox isn't a creature unless you control three or more permanents you don't own. At the beginning of your end step, exile the bottom card of each opponent's library face down. For as long as those cards remain exiled, you may look at them, you may cast permanent spells from among them, and you may spend mana as though it were mana of any color to cast those spells.

Your maximum hand size is eleven. Whenever Cecily, Haunted Mage attacks, you draw a card and you lose 1 life. Then if you have eleven or more cards in your hand, you may cast an instant or sorcery spell from your hand without paying its mana cost. Partner—Friends forever (You can have two commanders if both have this ability.)

Haste Whenever you cast your second spell each turn, untap target creature, then investigate. (Create a colorless Clue artifact token with "2, Sacrifice this artifact: Draw a card.") Partner—Friends forever (You can have two commanders if both have this ability.)

T: Add CC. Spend this mana only to cast artifact spells or activate abilities of artifacts. Partner—Friends forever (You can have two commanders if both have this ability.)

2, T: Choose target creature card in your graveyard that was put there from the battlefield this turn. Return it to the battlefield tapped. Partner—Friends forever (You can have two commanders if both have this ability.)

Menace Whenever Sophina, Spearsage Deserter attacks, investigate once for each nontoken attacking creature. (To investigate, create a Clue token. It's an artifact with "2, Sacrifice this artifact: Draw a card.") Partner—Friends forever (You can have two commanders if both have this ability.)

When Wernog, Rider's Chaplain enters or leaves the battlefield, each opponent may investigate. Each opponent who doesn't loses 1 life. You investigate X times, where X is one plus the number of opponents who investigated this way. Partner—Friends forever (You can have two commanders if both have this ability.)

T: Add C. 4, T: Investigate. (Create a colorless Clue artifact token with "2, Sacrifice this artifact: Draw a card.") At the beginning of your end step, if you sacrificed three or more Clues this turn, transform Havengul Laboratory.