Spell-like abilities are magical abilities that work similar to spells, but are not cast from a spellbook. Instead they typically have a fixed number of uses per day. Spell-like abilities rarely cause an attack of opportunity, require a concentration check, or can be counterspelled. In addition, since these are not cast from an arcane spellbook, they are never subject to arcane spell failure. If the ability is not identical to an existing spell, it is usually applied as an extraordinary effect and is thus not subject to dispelling. 10 + level + ability modifier