I'm actually pretty baffled about us not getting any legends with adventure in a set made for Brawl.
This is likely by design, as Adventure interacts oddly with the Command Zone mechanic.
In theory, if the adventure half is more relevant than the creature, you could cast the creature as an adventure, and then when it tries to exile itself on an adventure, simply send it back to the Command Zone, which would let you adventure again. While it could be interesting having a spell in the Command Zone, I bet they probably want to wait a bit on making that a thing, until they can dedicate a bit more time to getting it right.
It's also a bit of a flavor fail on the part of Adventures, because you send your Commander on an Adventure (which is weird itself, what leader abandons everyone at the time of need?), but then s/he DOESN'T go on the adventure, but just goes straight back home (going to CZ), but you still get the benefit of the adventure... that you flavorfully didn't actually go on.
Mechanically, it would be interesting though, as you'd have the choice between letting the Commander get exiled on the adventure so you can cast them for cheaper (just mana cost from exile), compared to sending them back to CZ, which would then increase the cost by 2, regardless which half you chose to cast.
There's also interesting portion of 'cheating' some Command Zone cost if the spell is cheaper than the creature, as you could cast the spell for more expensive, and split the cost over 2 turns. For example, imagine a Legendary Adventure Creature cost 4w, but the adventure cost W, and you have cast your Commander/Adventure twice, so you have a tax of 4. You could cast the spell for 4W, then the creature for 4W, Whereas just casting the creature straight from CZ would have cost 8W. This lets you still cast your Commander, even if you're on 5 lands, despite the tax, by splitting the cost over the two turns.
On the other hand, if the Creature half is cheaper, then you get the interesting question earlier in the game, as to whether you want to cast the creature half alone - knowing that it would make the Adventure cost more expensive later.
Either way, it shows there's quite a lot to consider in the design of a legendary creature with an Adventure, so I'm not surprised they didn't release one off the bat.
The final nail in the coffin is also probably that an Adventure legendary would want to be multi color, probably even 3 color, but the set itself is very focused on mono-colored interactions and cards. It could go into a Brawl deck, but that raises the complexity of a Brawl deck, which they would want more as introductory towards new players, I imagine.
In theory, if the adventure half is more relevant than the creature, you could cast the creature as an adventure, and then when it tries to exile itself on an adventure, simply send it back to the Command Zone, which would let you adventure again. While it could be interesting having a spell in the Command Zone, I bet they probably want to wait a bit on making that a thing, until they can dedicate a bit more time to getting it right.
It's also a bit of a flavor fail on the part of Adventures, because you send your Commander on an Adventure (which is weird itself, what leader abandons everyone at the time of need?), but then s/he DOESN'T go on the adventure, but just goes straight back home (going to CZ), but you still get the benefit of the adventure... that you flavorfully didn't actually go on.
Mechanically, it would be interesting though, as you'd have the choice between letting the Commander get exiled on the adventure so you can cast them for cheaper (just mana cost from exile), compared to sending them back to CZ, which would then increase the cost by 2, regardless which half you chose to cast.
There's also interesting portion of 'cheating' some Command Zone cost if the spell is cheaper than the creature, as you could cast the spell for more expensive, and split the cost over 2 turns. For example, imagine a Legendary Adventure Creature cost 4w, but the adventure cost W, and you have cast your Commander/Adventure twice, so you have a tax of 4. You could cast the spell for 4W, then the creature for 4W, Whereas just casting the creature straight from CZ would have cost 8W. This lets you still cast your Commander, even if you're on 5 lands, despite the tax, by splitting the cost over the two turns.
On the other hand, if the Creature half is cheaper, then you get the interesting question earlier in the game, as to whether you want to cast the creature half alone - knowing that it would make the Adventure cost more expensive later.
Either way, it shows there's quite a lot to consider in the design of a legendary creature with an Adventure, so I'm not surprised they didn't release one off the bat.
The final nail in the coffin is also probably that an Adventure legendary would want to be multi color, probably even 3 color, but the set itself is very focused on mono-colored interactions and cards. It could go into a Brawl deck, but that raises the complexity of a Brawl deck, which they would want more as introductory towards new players, I imagine.
Retired EDH - Tibor and Lumia | [PR]Nemata |Ramirez dePietro | [C]Edric | Riku | Jenara | Lazav | Heliod | Daxos | Roon | Kozilek