Really cool premise! But even without the trinket text, this seems way too good at its current cost- at the very least 2RR, but "2RR with double strike and another upside" is generally 2/2, like with Hound of Griselbrand.

Trinket text? If you mean the second part, the phrasing of it means that if it kills a blocker with first strike damage, the second strike damage goes through to its controller.

You're right that it's too good with that cost, though. Given that the Hound comes back as a 3/3, and that this is a smaller upside, I think that one more power is probably fine. Though I suppose a 3/1 isn't out of the question.

...Or I could just make it cost 2RG, I suppose.

3-power double strikers are always rare, though. And generally 5 mana unless you're talking about a gold mythic (Kalemne, Disciple of Iroas, Rafiq of the Many). 2-power double strikers are rare if they have a chance of sharing their double strike with other creatures or of getting bigger, but uncommon if not.

You can get 3 power of double strike at uncommon, but only if the double strike is conditional or unreliable in some way (Ordruun Veteran, Spiraling Duelist).

Fair enough then. Changed.