A · Fundamentals · §3
The shuffled 39 contains 27 units built around the 5-to-6 conversion, with an intentionally empty 4-Might tier.
＋ Bring in (tap to add copies)
− Take out
27 shuffled units.
From the guide — §3 Deck Architecture
The strongest natural Hook conversion is Glasc Mixologist or Vi at 5 Might into Harnessed Dragon or Ruined Rex at 6 Might. Dragon Form allows any smaller body to enter that same tier.
Harnessed Dragon or Ruined Rex can become Rift Herald or Thousand-Tailed Watcher. The payoff is substantial, but the deck contains only three seven-Might units.
Karthus can activate Hook, but there is no printed four-Might unit to upgrade into. Hooking away Karthus gives access only to units costing three Might or less.
That can still be correct when: Karthus has already multiplied sufficient value; Karthus is exposed to removal; you need another body immediately; the five-card selection improves future draw quality; or you need to trigger a different Deathknell. But it is not a genuine upward conversion.