Laurent -

Added "untap all" to the parser (not tested but should work since it is the same as tap all)
Modified "cantbeblockedby" also still don't function properly, atm it cause the creature to be "unblockable"... Should work, I don't get it !!! (Why ???)
Also added Seedborn Muse (like all the Muse a very Powerfull card), especially as combo with cards that "DOESNOTUNTAP" during your untap phase...

projects/mtg/bin/Res/sets/10E/_cards.dat

@@ -659,7 +659,7 @@ mana={3}{U}{U}
 text=Elven Riders can't be blocked except by Walls and/or creatures with flying.
 id=135266
 name=Elven Riders
-auto=cantbeblockedby(creature[-walls;-flying])
+auto=cantbeblockedby(creature[-flying])
 rarity=U
 color=Green
 type=Creature
@@ -2148,6 +2148,18 @@ subtype=Serpent
 toughness=6
 [/card]
 [card]
+text=Untap all permanents you control during each other player's untap step.
+id=129722
+name=Seedborn Muse
+rarity=R
+color=Green
+type=Creature
+mana={3}{G}{G}
+power=2
+subtype=Spirit
+toughness=4
+[/card]
+[card]
 text=Discard a land card: Seismic Assault deals 2 damage to target creature or player.
 auto={S(land|myhand)}:damage:2 target(creature,player)
 id=129884