[Set Release] The Lost Caverns of Ixalan roundup

[RivalRowan]

Hi, just putting a roundup of the new symbols courtesy of The Lost Caverns of Ixalan (LCI) release.
For the first time, WotC has published a full Arena Release Notes article so most of the symbols can be found there.

Arena Ability Symbols:
LCI has one new keyword ability, two new keyword actions and two new ability words.

- Craft is an activated ability that lets you transform a permanent by paying mana and exiling one or more cards of a certain quality (from either the battlefield or the graveyard). The bottom part of the spanner is cut off in this image but not in-game.

- Discover is a keyword action that acts as a fixed version of Cascade. You exile cards from the top of your library until you hit a card with mana value less than or equal to the discover number. You may cast that card and the rest go to the bottom of your library in a random order.

- Descended is a bit of a headache because it's four different things being used in two different ways. You've got:

• Descended - This is the keyword action (or maybe player designation) and means "A permanent card went to your graveyard this turn from anywhere". It's used to trigger abilities and effects.
  
• Descend 4 and Descend 8 - both of these can be thought of as Threshold or Delirium variants. If you have four or eight permanent cards in your graveyard you get a bonus effect (or a bigger effect). They are both ability words.
  
• Fathomless Decent - this is another ability word that just means the effect gets bigger the more permanent cards are in the graveyard. Unlike the other three, this one scales with graveyard size.
  

For the purposes of Mana, the pick-axe icon is used for both cards with descended effects and cards with Fathomless descent. With Fathomless descent it also gets a numeric counter, to indicate the size of the descent.

Arena Exclusive Counters:
LCI introduces a number of new counters to Arena but only one of them is receiving a counter symbol - Finality counters.
Finality counters have rules baggage, so when a permanent with a finality counter on it dies, it's exiled instead.

As noted in #116, Arena is using the same symbol for Finality counters as the physical punch-out cards. MTGO should be using the same symbol but we won't know until the set is released.

Misc:
The set also reuses Explore and Stun counters, but there doesn't appear to be any changes in those icon from their last uses.