J0N4TH4N - (MRD) added Looming Hoverguard, tested both automatically and manually, works great, and yes, it does move to the top of library just in case you are wondering

projects/mtg/bin/Res/sets/MRD/_cards.dat

@@ -627,6 +627,20 @@ power=10
 toughness=10
 [/card]
 [card]
+text=Flying. When Looming Hoverguard enters the battlefield, put target artifact on top of its owner's library.
+target=artifact
+auto=moveTo(ownerLibrary)
+id=48114
+name=Looming Hoverguard
+rarity=U
+mana={4}{U}{U}
+type=Creature
+subtype=Drone
+power=3
+toughness=3
+abilities=flying
+[/card]
+[card]
 text={W}, {T}: Regenerate target artifact.
 auto={W}{T}:regenerate target(artifact)
 id=46071

projects/mtg/bin/Res/sets/MRD/todo.dat

@@ -679,19 +679,7 @@ power=2
 subtype=Myr
 toughness=2
 [/card]
-[card]
-text=Flying   When Looming Hoverguard enters the battlefield, put target artifact on top of its owner's library.
-auto=moveTo(ownerLibrary) target(artifact)
-id=48114
-name=Looming Hoverguard
-rarity=U
-mana={4}{U}{U}
-type=Creature
-subtype=Drone
-power=3
-toughness=3
-abilities=flying
-[/card]
+
 [card]
 text=At the beginning of your upkeep, the player with the lowest life total gains control of Loxodon Peacekeeper. If two or more players are tied for lowest life total, you choose one of them, and that player gains control of Loxodon Peacekeeper.
 id=48180

projects/mtg/bin/Res/test/_tests.txt

@@ -138,6 +138,7 @@ lhurgoyf.txt
 liability.txt
 lifeforce.txt
 living_lands.txt
+looming_hoverguard.txt
 lord_of_the_pit.txt
 lord_of_the_pit2.txt
 master_of_etherium.txt

projects/mtg/bin/Res/test/looming_hoverguard.txt

@@ -0,0 +1,19 @@
+#comes into play and move target
+[INIT]
+FIRSTMAIN
+[PLAYER1]
+hand:Looming Hoverguard
+manapool:{4}{U}{U}
+[PLAYER2]
+inplay:Dragon Engine
+[DO]
+Looming Hoverguard
+Dragon Engine
+[ASSERT]
+FIRSTMAIN
+[PLAYER1]
+inplay:Looming Hoverguard
+[PLAYER2]
+library:Dragon Engine
+life:20
+[END]