Isa: (I: Ice.) A challenge or frustration. Psychological blocks to thought or activity, including grievances. Standstill, or a time to turn inward and wait for what is to come, or to seek clarity. This rune reinforces runes around it. Isa Merkstave (Isa cannot be reversed, but may lie in opposition): Ego-mania, dullness, blindness, dissipation. Treachery, illusion, deceit, betrayal, guile, stealth, ambush, plots.
Isa, the Ice, is the simplest rune of Norse alphabet. This is the rune of stability and stagnation, but mostly (and what is more important) – the symbol for the potential underneath the seemingly sound surface (like living water under thick winter ice). So it means not only the period of a standstill, but also the progress you will make after it.
The tree for Isa is ivy.