Can someone explain me how this spell works with an example? I still don't get it.

Contingency is a trigger for another spell.  You set the trigger, for example, your character becomes severely injured, say, below 25 hit points.  You choose another spell that is cast if the trigger goes off, for example a teleport.  If the triggering condition is met (dropping to low health) a teleport spell goes off teleporting you to a place you already selected.  Then while the contingency is active, if you get badly injured the spell goes off without you doing anything further.

So a giant comes over and stomps on your wizard, the triggering condition is met, the contingency fires off, casting teleport, and your wizard escapes further pummelling so long as there isn't something blocking the teleport.

It doesn't have to be teleport, you could set it up to cast a fireball on yourself when someone sneezes on you... pretty much anything you want whether it makes sense or not.

Thank you for responding, it has helped me. So does this eat up three spell slots? how does that part work, would it be possible for you to give me an example?

It uses two spell slots when cast: a 6th-level slot for Contingency itself, and a lower-level slot for whatever other spell you wish to cast it with. Here's one use-case example:

Your bard wakes up, and in preparation for the day, casts Contingency and Raise Dead together. He uses both a 6th-level spell slot and a 5th-level spell slot to do so, and sets the trigger to go off whenever he actually dies (not just when his HP drops to 0.) Nothing happens immediately, except that the Contingency spell is now active on him.

He goes through his day, goes to bed, wakes up, etc. Five days later, his entire party is in combat with a coven of hags, and they find themselves losing. The team druid--the only other healer in the party--has just dropped to 0 HP, and your bard is already at 0 HP with two failed death saving throws. Just before his turn comes around, a hag injures the bard again, causing him to die.

Immediately, the Contingency goes off, and the stored Raise Dead spell is cast on the bard. He is brought back to life with 1 HP, and since it's his turn, he immediately stands, then Disengages, takes a defensive position and upcasts Healing Word on the druid. Her turn is next, and she immediately casts Mass Cure Wounds, giving everyone just enough HP to finish the fight and take out the remaining hags.

EDIT: One last note, Contingency doesn't do any concentrating for you, unlike Glyph of Warding. So if you have it store, say, Greater Invisibility, you'll still have to concentrate on the spell once it's activated. Source: https://rpg.stackexchange.com/questions/105220/does-a-concentration-spell-still-require-concentration-when-triggered-by-conting

raise dead has a casting time of 1hour and contigency requires a spell with a cast time of 1 action

Good catch, forgot about the casting time of Raise Dead. A better example would be Revivify, which is third level and only takes 1 action to cast.

Idk how to delete comments.

 Would anyone be opposed to up casting this to allow higher level spells to be stored with it?

Does the used spell slot for the stored spell remain used until the long rest after the trigger (or Contingency times out) or does it come back after the first long rest after the ritual, whether it’s triggered or not?

* - (a statuette of yourself carved from ivory and decorated with gems worth at least 1,500 gp)

Does it count if the statuette material component is stored in a PC spellcaster's Bag of Holding or Portable Hole?

I.T. 

Quote from Iron_Theurge >>

* - (a statuette of yourself carved from ivory and decorated with gems worth at least 1,500 gp)

Does it count if the statuette material component is stored in a PC spellcaster's Bag of Holding or Portable Hole?

 

I.T. 

 The material component is required for the casting of the spell. Unless otherwise noted, it is not needed ever again. Some spells use it and require certain things to be done with their components though. In this case, you have the statuette to cast and then you can stash it somewhere else. 

Quote from Caladrel >>

Quote from Iron_Theurge >>

* - (a statuette of yourself carved from ivory and decorated with gems worth at least 1,500 gp)

Does it count if the statuette material component is stored in a PC spellcaster's Bag of Holding or Portable Hole?

 

I.T. 

 The material component is required for the casting of the spell. Unless otherwise noted, it is not needed ever again. Some spells use it and require certain things to be done with their components though. In this case, you have the statuette to cast and then you can stash it somewhere else. 

 
Veeerrry end of the spell: "Also, contingency ends on you if its material component is ever not on your person." 
I'd say that another dimension might not count, but extradimensional space has always been iffy. DM discretion, I think.

Quote from RodTheBard >>

Your bard wakes up, and in preparation for the day, casts Contingency and Raise Dead together.

  I think a better option (when possible) would be to use your leftover 6th level slot and whatever you have left to cast it before a long rest. That way the cost isn't as high and you can just recast it every few days if you don't end up activating it.

How specific can we get with this?

For example, could one of my players cast Contingency with Resilient Sphere, with the trigger being: "When I am about to get hit by the breath weapon of a dragon" and have the sphere appear and negate the damage? 

I would rule yes, but it's a little weird with the wording. Could be construed as vague. 

What I wonder is it says a 5th level spell or lower, could that spell be cast at 5th level when it is a 3rd level spell to store a more powerful version?

Quote from Lord_Jeeves_Of_The_Assless_Chaps >>

How specific can we get with this?

For example, could one of my players cast Contingency with Resilient Sphere, with the trigger being: "When I am about to get hit by the breath weapon of a dragon" and have the sphere appear and negate the damage? 

I would rule yes, but it's a little weird with the wording. Could be construed as vague. 

 As I read it, there are no limitations on the specificity allowed. You could have it activate a Dimension Door "after the sun reaches its zenith on the day of the sabbath, when: a) I fail my saving throw against the breath weapon of the Green Dragon Cyan Bloodbane, or would be hit by said breath weapon with less than 50 HP, such that I am teleported away before taking damage, b) when I would be hit by an attack from said Green Dragon while my HP is less than 69, such that I am teleported away before taking damage, or c) when I would be hit by a critical hit by a CR 13 or higher creature, such that I am teleported away before taking damage. Alternatively, if I bite the inside of my right cheek while I have one eye opened with the other closed, the contingent spell should activate." (As for the last part, I like to always have some weird thing that I can do to activate it if I need it without the condition. This can, of course, only be activated on the caster's turn) As a DM, I rule that pretty much anything is fair game (must be delivered to me in writing, though), and if it would go off and the player forgets, then the spell is lost (Says that it must be activated, and going back in time to replay would should have happened is too annoying).

Having it activate when you would be hit by something but be able to activate before you take damage is debatable, but I think makes sense that right as the first molecule of the attack hits the first molecule of the character, the spell would activate, and I get to describe it as a really cool moment. Due to the setup required, I don't find it to be at all gamebreaking. I find that it's a bit of a "haha, I saw that coming YESTERDAY!" kind of moment, and totally worth it.

Quote from CREEPER062501 >>

What I wonder is it says a 5th level spell or lower, could that spell be cast at 5th level when it is a 3rd level spell to store a more powerful version?

 Yes, it doesn't specify otherwise. As long as you expend the higher level slot when you cast it. Although, it can only affect you, so you cannot use a 5th level Invisibility to make other people invisible too. I've also taken "The contingent spell takes effect only on you, even if it can normally target others" to mean that if you use it with Fireball, it still only damages you because of that clause.

You cast it along with the spell it’ll use and set conditions. When those conditions are met then the spell you chose activates

Would this still work if you take it through an anti-magic field?

Yes, because any ongoing magical effect is suppressed is an anti-magic field, but not dispelled. So if a character has Contingency cast and walks into an anti-magic field then the Contingency basically just can't trigger. If they then move or are moved out of the field, then the triggers count again.