Time Condition

You can use the spell contingency on every single spell you have prepared each day (once), doing so when you prepare your spells for the day with a dedicated material component for each spell and following the contingency spell's rules unless otherwise stated here. Each one of those spells must have their own condition, as long as that condition doesn't rely on contingency itself (such as "cast this spell when my contingency triggers"). If one or more spells would trigger at the same time, or in response to the same thing, they all fail to cast and are expended. You can't trigger your own contingency through means you take, though your contingencies may be of any level spell you can cast. They can also target as the casted spell normally would, allowing them to occupy space, target creatures other than you, and other such things, such as their range. (Self spells can still only target you). All aspects of the spell must be decided upon when it is prepared, such as it's intended target for spells that target a creature or object, or it's exact space and dimensions for a spell like Wall of Force (Ex. a 10x10 wall 10 feet in front of me). The only spell you cannot use with this ability is ones that require the casting of another spell as part of it's effect, such as one of the modes on Glyph of Warding. 

Creatures can still detect your Contingency around your body with things like detect magic, and the magical connection is has to it's material component. If casting dispel magic on you directly, the contingency is not affected, but if cast directly on the related material, that instance, and all instances of contingency that share a spell school in their prepared spell end. This also happens if the material component is specifically destroyed, such as with a disintegrate spell or another ability that specifically states it destroys objects. If your contingency would have multiple concentration spells active at once, you may choose which one ends immediately. (Clarification: Contingency spells take effect, so they are not being cast when triggered, and some rule this as lack of need for concentration). Self spells cast with this ability may be applied even if you already have a self spell of the same name active, gaining the full benefits of both.

Due to the fact that spells in contingency appear instantly with no warning, they are difficult to predict. Attack rolls with them have advantage, and saving throws against them have disadvantage.