Cheapest priced copy (The Brothers' War): $0.99 at Card Kingdom, near mint, their price list as of .
Surge Engine 
Artifact Creature — Construct · 3/2 · Mythic · The Brothers' War · #81
Defender
{U}: This creature loses defender and gains "This creature can't be blocked."
{2}{U}: This creature becomes blue and has base power and toughness 5/4. Activate only if this creature doesn't have defender.
{4}{U}{U}: Draw three cards. Activate only if this creature is blue and only once.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
5 printings · $0.99 to $5.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| The Brothers' War | 81 | Mythic | $0.99 | $0.99 |
| The Brothers' War | 320 | Mythic | $0.99 | $1.49 |
| Game Day Promos | 9 | Mythic | — | $5.49 |
| The Brothers' War Promos | 81p | Mythic | $1.99 | $1.99 |
| The Brothers' War Promos | 81s | Mythic | — | $1.29 |
3 rulings from Wizards of the Coast
- 14 October 2022If a Surge Engine whose last ability has been activated leaves the battlefield and comes back, it's a new object on the battlefield and its last ability can be activated again (once it's blue, of course).
- 14 October 2022Surge Engine's last ability can be activated only once per game, not once per turn.
- 14 October 2022If Surge Engine loses defender in some way other than its first ability, its second ability may still be activated. Likewise, if it becomes blue in some way other than its second ability, its last ability may still be activated. Note that an effect that allows a creature to "attack as though it didn't have defender" doesn't actually cause it to lose defender.