Double Versing = if you activate Yisan, hold priority, untap Yisan and activate again, you get two tutors for creatures of the latest verse. For example, your Yisan is at 2 counters. You activate Yisan, hold priority, untap Yisan, then activate Yisan again. Yisan is now at 4 verse counters and you can search for two 4-cmc creatures.
Main paths:
1) Standard path: This is path you want to take in most situations unless you need to find answers / get interrupted by opponent / you can get faster with using your hand- Quirion Ranger, Priest of Titania, Fierce Empath for Craterhoof Behemoth
2) Combo path: If you have 1CMC elf and enough lands, then really good path to win turn 5 is: Wirewood Symbiote, Wall of Roots and Circle of Dreams Druid, then you can win in your turn by combo with Temur Sabertooth. You should have 5 mana when you use Yisan for second time, so you search for Wall of Roots and it will give you extra mana to use yisan again.
3) Toolbox path: There are games where you need to use multiple verse counters as toolbox. In games like that you just find whatever is needed and end game might be some big creatures from your deck for example Questing Beast / Elder Gargaroth, but this is based on your hand a lot.
Choices:
1 CMC
Arbor Elf if you have Wild Growth / Utopia Sprawl.
Quirion Ranger / Wirewood Symbiote for untap.
Sylvan Safekeeper if you need protection.
Allosaurus Shepherd this card is just amazing, you can search it if you want to cast something big from hand, or if you have a lot of elves, so you can give everyone Allosaurus and attack opponent.
Boreal Druid if you need colorless mana for Thought-Knot Seer.
Skyshroud Ranger decent choice, if you have some lands on hand and also Quirion Ranger / Scryb Ranger.
Other Mana elves if you need some extra mana.
2 CMC
Priest of Titania / Rofellos, Llanowar Emissary if you can use a lot of mana, this is always good choice.
Phyrexian Revoker is great answer against a lot of combo decks, walkers or some artifacts.
Wall of Roots maybe when you need something on 3 CMC and you need extra mana to use Yisan again or when you need good blocker.
Wall of Blossoms solid blocker + cantrip.
Sylvan Caryatid hexproof blocker can be very usefull against mono-red.
Scavenging Ooze just grave hate and lifegain.
Scryb Ranger is not just for untap. You can use protection from blue for blocking Kraum / Kess or some random blue creatures.
Fauna Shaman you search for her as response, when Yisan would be removed from battlefield.
Elvish Visionary is good to search as reaction against mass removal, so you have some value from it at least.
Kraul Harpooner removal against flyers, but can also be searched for trade with big attacking creatures, because he gets that +X buff even without any flyers on the battlefield.
3 CMC
Augur of Autumn not really good target for Yisan, but I search for it a lot with Woodland Bellower.
Circle of Dreams Druid is really good to search as double-verse along with Fierce Empath, because Circle of Dreams Druid will usually give more mana than Rofellos, Llanowar Emissary / Priest of Titania, so it is easier to cast Craterhoof Behemoth.
Courser of Kruphix good blocker and life gain.
Eternal Witness when you need to get win condition from graveyard.
Reclamation Sage when you need removal for enchantment or artifact.
Endurance can be used as grave hate on opponent, but also on yourself when you want to search something, but it is in your graveyard. Second reason is usually used from hand, because Eternal Witness is just better.
Fierce Empath usually just go for Craterhoof Behemoth, if you can win from it.
4 CMC
Thought-Knot Seer I like to search for him a lot. When i know opponent has something annoying in hand or when i want to win with Craterhoof Behemoth and want to be sure opponent doesn't have any answer against it.
Questing Beast to finish opponent, kill planeswalker, or as toolbox against Glacial Chasm or other prevents.
Temur Sabertooth removal protection and combo piece.
Obstinate Baloth quite big creature that gains life, so solid against aggro.
5 CMC
Whisperwood Elemental if you have enough creatures on the battlefield, then he is really good option to secure you a win, because wrath effects will not save your opponent at that point, but he is also good against aggro decks, because you just creature free tokens each turn, which might turn into usefull creatures later. Also the fact that they are colorless can come handy against protections.
Deep Forest Hermit really good against aggro decks and have some valid synergies.
Elder Gargaroth this is MVP against aggro decks.
6 CMC
Primeval Titan not really target for Yisan, but there are valid targets for him, so he can work as another solo-card win.
Woodland Bellower this is card you will usually choose when you get on this CMC. He is just so good.
Sawtusk Demolisher I wasn't sure about this card, but he turned out as really good card. You will never search for him with Yisan, because you need to get him to your hand. Good thing is that Fierce Empath can find him. When you mutate you can either destroy some annoying card, opponent's land, or against aggro decks I often destroy my own land to create that 3/3 beast under my control.
