1. Master Gremlins: + to health and + to initiative (the latter is better)
2. Gargoyles: + to speed
3. Golems: rarely, but it's still possible to get + to "battle spirit" if you have the "machine loyalty" skill, or + to speed/initiative if you get the "golem march" skill.
If necessary, I disassemble the mini-artifacts back, as there is no penalty for such conversion: assembled - war, resources needed - disassembled :)