Just made a deal with a fae, against my better judgement hahaha. Can't say "THE" for 30 days.

Can I use it to destroy Britannia? and does it come with a familiar named C.C aka C2?

If Geas is a known spell for a player, does that mean they would also know that the spell can be undone with remove curse, greater restoration, and wish?

This spell comes from Irish/Celtic myth, where many heroes were subject to geasa (the plural of geas), and they were usually things the recipient was supposed to not do. By accepting the geas (sometimes with no choice in the matter!) the recipient receives a favour or power.

An example from myth includes the hero Cúchulainn, who had two geasa placed upon him - one, that he could never refuse hospitality offered; and the second, that he could never eat dog meat.  He met his doom after being offered dog meat, which he couldn't refuse. Contradictory geasa like this were quite common.

Casting time 1 minute? So, not a combat spell, then?

can a target willingly fail the save, if your making a pact or something.

Quote from JenniCharming >>

"It's a pretty good spell, the only issue is the 1 minute casting time."

Nah, the biggest issue with this spell is that it only triggers 1 time a day. 5d10 only averages out to 27 damage, so there is no real threat of death for non-compliance to a character above 5th-6th level. If an NPC casts this on a party member, a party even without a cleric can just take a short rest to negate the damage and otherwise continue on there merry way. Triggering only once a day this spell is toothless. In my games, I run variant rule striking , "but no more than once each day".

I'd add this to Warlock honestly.

I have half a deck of many things, it is only the bad cards. "Pick a card, any card"

For sociopaths like me:

>17 lvls in Wizard

>Take the Wish spell

>3 lvls in Sorcerer

>Take the Subtle Spell Metamagic option

>Cast this spell in a single Action using Wish, although it's capped at 8th level according to RAW so you only get its usage for a year maximum

>Use Subtle Spell during the casting so as to make it entirely undetectable. The spell never explicitly states that the person knows they've been Charmed either lol

>If it's cast on royalty or an especially powerful magical creature, you get their free services and Advantage on any Charisma checks towards them, allowing for anything from immediate servitude to long-term social manipulation. 

Does the command need to be issued during the 1 minute or can it be issued during the 30 days?

I'm going to use this spell to force a captured enemy to return to his army and be my spy for 30 days. I'll use the "Sending" spell to check in with him regularly so he can feed me inside info about the movements/plans of the army and give him any further instructions if I want. 

A bbeg who is just casting geas at ninth level on everyone so that for example when he says bop they all attack the adventurers

So, dispel magic doesn't remove Geas as per this?

"You can end the spell early by using an action to dismiss it. A remove curse, greater restoration, or wish spell also ends it."

I disagree on the "instead of the Druid" Part, geas is a "feature" of celtic mythology, which druids come from aswell, so they are the ones that have the best reason to have this spell

Wasn't it three geasa  he was placed under, or was it three times he was offered dog meat?

So if you attack a creature under the affect of geas, and you are the caster, does this break the geas? 
I ask becasue one of my players used the geas spell, then proceeded to attack the person. The charmed condition states that a charmed creature cannot attack the charmer, therefor the creature just has to take the damage. 

Any thoughts on this