Tainted Grail: Conquest

The Summoner, is in my opinion, the easiest class in the game to play. Summoners cannot directly deal damage to the enemy, but instead fight using minions, with the effect triggered every time the minion is activated. The Summoner ability is to activate a minion once for 0 energy, which is a card you will use heavily. The Summoner Ultimate charges with 1 charge each time a minion is activated, with a full 9 charges adding 3 levels to the chosen minion when used. Try and only use it when it is fully charged. There are 4 minions you can use. which are:

Golem: Attracts all attacks towards itself. Activating the Golem will heal it for the amount shown above its head
Fae: Gives you 1 Ultimate charge per Fae level.
Abomination: Deals a single attack to all enemies.
Wyrm: Deals 2 attacks randomly that also lower enemy Armour by 3 per attack.

You can choose any but the Fae to always be spawned when you begin a battle when you select the Summoner class. I would recommend always starting with a Golem, as it protects against attacks to your HP directly. Try and avoid promoting the Golem if you can, as the HP gain is not worth the extra damage it deals to the Summoner per attack (1 per Golem level). To avoid taking this damage, always try and have a Barrier around the Summoner if you can, your deck starts with 3 +10 Barrier cards in and these should be used whenever you cannot activate minions anymore this turn, but still have energy. You can summon up to 4 minions at once, but I would recommed only using 2. This is because whenever there are attacks that hit all friendly targets, the Golem will absorb all the damage and probably die, which leaves you and your other minions vulnerable.

To deal damage, your second minion should either be Wyrm or Abomination. Wyrm is the better choice, as it can reach some crazy high damage numbers when you keep promoting it, as well as every attack making the enemy take more damage from the next. If you know there are no enemies with group attacks, you can have both Wyrm and Abomination, switching between the two as you think is appropriate (Abomination is only really good against 3+ enemies). Whenever you have a promotion card, use it on the Wyrm/Abomination, unless you can also activate the minion enough times that you use all your energy.

The priority for combat is as follows:
Heal or summon new Golem
Place Barrier on Summoner
Summon new Wyrm/Abomination
Promote Wyrm/Abomination
Buff any minion
Activate Wyrm/Abomination

If you follow this formula and fight every battle you see, you should reach level 20 in the third area, just before you fight the 3rd guardian.

Good cards to grab when you see them are:

For using on Golems:
Mystical Blood: Minion heals 50% of missing HP at the start of each turn (1 Energy)
Oversaturation: Activate the minion every time you begin a turn (2 Energy)
Surge: Fully heal the minion and give it 25 Barrier (1 Energy)
Existence: Raise the minion Max HP by 50 and heal it for 15. (0 Energy)

For using on Wyrm/Abomination:
Advanced Promotion: 2 Promotions (1 Energy)
Dark Rites : 1 Activation (0 Energy)
Fury: Each turn, the minion gets 10% more damage (0 energy) (stackable)
Self Awareness: Promote the minion at the beginning of each turn (2 Energy)
Advanced Activation: Activate a minion, but will return so can be used again once more. (1 Energy)
Acid Saliva: Each hit permanently drops enemy Armour by 5 (0 Energy) (stacks with Wyrm natural -3)