Landfall and extra-land-drop decks. Any effect that lets you play a second land in a turn — Exploration, Azusa, fetch lands — turns Tannuk into a repeatable card draw engine as well as reach.
Fetch-land shells. Cracking a fetch land and playing your natural land drop in the same turn is the cleanest, most consistent way to trigger the card draw every turn.
Gruul group damage. Even without doubling land drops, the passive one-damage ping to every opponent adds up over a long game and closes out a slow race.
How it does in Commander
As the commander
As the commander, Tannuk gives a lands-matter Gruul deck a reliable card-advantage engine it can build fully around — every extra land drop effect in the 99 becomes a draw spell as well as reach, which rewards a deck that goes all-in on doubling land drops.
In the 99
It's a strong support piece in any red-green landfall shell even without being the commander, quietly turning fetch lands and ramp spells that put lands into play into extra value on top of their usual job.
Formats it's strong in
Lands-matter and landfall decks. The card is built specifically to reward decks that already want to play two lands a turn, so it slots in as a bonus rather than a new plan.
Grindy, long games. One damage a turn and occasional extra cards compound the longer a game runs, which suits a deck built to go the distance.
Formats it's weak in
Decks with no way to double land drops. Without an extra land drop effect, it only ever hits the first trigger and never draws a card, leaving it as a minor damage source.
Fast, aggressive pods. The value is incremental rather than immediate, which is a poor match for a table trying to close games out by turn five or six.
Synergistic cards
Exploration — The classic extra-land-drop enabler that guarantees Tannuk's second trigger, and its card draw, every turn it's active.
Fetch lands — Cracking one and playing a natural land drop in the same turn is the easiest, most repeatable way to hit two land plays.
Azusa, Lost but Seeking — Grants up to two extra land drops a turn, which reliably triggers Tannuk's draw and then some.
Scapeshift — A single spell that fetches a pile of lands at once — each one triggers Tannuk's damage, and the second onward triggers the draw too.
Is it worth the price?
As a recent set release, Tannuk is inexpensive and a reasonable pickup for any lands-matter Gruul deck — worth owning if the rest of the deck is already leaning on extra land drops, and skippable otherwise.