In between your two turns, I untap, upkeep, Draw, Done.
I was actually off by a turn/card - so I do have a play this turn and I didn't have to discard... (This is my 9th turn as I count, correct?)
I think what happend was I didn't account for the untap, draw, go... so it made my count off... but I'm certain this is correct... I'm equally certain your library count is off...
After the turn you attack (right now), I play...
Untap, Upkeep, Draw
Play Swamp, Play Guardian Beast, Done
Melkor: 20
Hand: 5
Library: 50
In Play:
(U) (U) (U) (U) Mountain x4
(T) (T) Island x2
(U)
Shifting Wall (3/3, Defender, ~ comes into play with X +1/+1 counters)
(T)
Primal Plasma (3/3, (when ~comes into play choose whether it is 3/3, 2/2 Flying, 1/6 Defender)
(U)
Avalanche Riders (2/2, Echo, Haste, when ~ comes into play, destroy target land)
Invisibility Enchanting Primal Plasma (Enchanted Creature cannot be blocked except by walls)
Graveyard:
RFG:
---------------------------
BigBlue: 17
Hand: 6
Library: 46
In Play:
(U)
Pentad Prism (Remove a counter: Add 1 Mana of any color) (0 Counters)
(U)
Aether Spellbomb (1, T, Sac ~: Draw a card; U, T, Sac ~: Return target creature to it's owners hand)
(T) Plains
(T) Swamp
(T)
Leaden Myr (1/1; T:B)
(T)
Iron Myr (1/1; T:R)
(U)
Arcbound Wanderer (
5/5; Modular) (5 +1/+1 Counters)
(S)
Guardian Beast (2/4; As long as ~ is untapped, Noncreature artifacts I control cannot be enchanted are indestructible and cannot be controlled by opponents)
Graveyard:
Island
RFG: