|This is a common phrase among the community when discussing deck strategy. It may not appear on runes as rule text.|
Alternative damage refers to non-physical damage. Physical damage is the most popular damage type by far, and so abilities such as Resistance - Physical and Rock Eater can create a big problem for decks with only Physical damage. Thus it is common for players to talk about needing "Alternative damage" in a faction or a theme to reduce this issue.