Promo lets you pay 1-2 spell points, 1 quick action, 4 mana and neck slot for no payback, just the ability to spend 1 full action for +3 mana.
We are assuming the officially released Meditation Amulet is the promo. I know we had a Director saying promos aren't beta-testing and will be released exactly as is. But Ballista, Iron Guard, Akiro's Favour etc suggest that they will make changes before release.
The Druid is best placed to use it as she has vines, 2 Tree spawnpoints, 6 Pods and Felella. She does not need to move as she has vine range QC spells, her spawnpoints and Pixie enchantments. But it limits her to plant spells only, there is no plant Dispel or plant Teleport.
The Necromancer has his 2 spawnpoints too so he could use it for a creature build. Perhaps a Skeleton Fort which is very sedentary with Knight guards and Archers adjacent to Altar of Skulls in the centre of a corner "L" (where Mort and Acolytes are also placed, surrounded by 2 Wall of Bones). But the set-up time for that Fort is so long.
We are getting excited about new cards but they are spawnpoint-driven. We all know an aggressive Warlock, Forcemaster or Beastmaster can currently shred a spawnpoint opening. There has been no new tech spoilt to make spawnpoints more viable. The only hope from the list is a beefed-up Meditation Amulet.
The promo is simply strictly worse than Moonglow's no action +1 mana per turn. If they raised the ability to 5 per full action then it would be played in mid range spawnpoint builds. But as it is? I just can't see it being preferred.