Creature — Kraken 4/8, 5UU (7)
Rare
Shroud
Isleback Spawn gets +4/+8 as long as a library has twenty or fewer cards in it.
The more deadly the lake monster, the shorter the tale.
Illus. Mark Tedin

5/1/2008: It doesn't matter which library has twenty or fewer cards in it, and you don't have to specify a library. If multiple libraries have twenty or fewer cards in them, Isleback Spawn will still get its bonus only once.
Legal in Vintage (Type 1)
Legal in Legacy (Type 1.5)
Legal in Classic (MTGO)
Legal in Commander
Legal in Modern