Most played cards in Fetchland Tendrils:

34 Decks
Lion's Eye Diamond
136 copies - 4 average
Brainstorm
132 copies - 3.88 average
Dark Ritual
132 copies - 3.88 average
Polluted Delta
126 copies - 3.71 average
Cabal Ritual
124 copies - 3.65 average
Infernal Tutor
123 copies - 3.62 average
Lotus Petal
117 copies - 3.44 average
Mystical Tutor
111 copies - 3.26 average
Flooded Strand
105 copies - 3.09 average
Ill-Gotten Gains
89 copies - 2.62 average
Dark Confidant
83 copies - 2.44 average
Orim's Chant
82 copies - 2.41 average
Tendrils of Agony
81 copies - 2.38 average
Underground Sea
73 copies - 2.15 average
Leyline of the Void
68 copies - 2 average
56 copies - 1.65 average
Ponder
49 copies - 1.44 average
Intuition
46 copies - 1.35 average
Echoing Truth
41 copies - 1.21 average
Duress
34 copies - 1 average