From now on, I will post my custom cards in here. 
I will try to give some explanations of the ideas I have while designing the cards.
Some cards also have some balance thought in their text. It is called theorycrafting balance 
Nurturing Beast is a faster Whale (6 lands instead of 8) with the downside of giving a buff to opponent creature. You can also decide to swallow one of your creature to gain a slow buff. The price wouldn’t make it a good target for a sac deck but if you have some mobility cards in hand the tradeoff can be lower by a lot.
The Brick Glutton is design to counter structure deck. It fits red theme and was designed with Forgotten Library in mind. You can also swallow your own structure when you think you had enough of it. A strong downside of this card is the reality check of swallowing a Crystal Flower. I guess it couldn’t as Swallow do not work agaisnt Swallower but if it is able to it could cause some issues.
The Dying Bleech fits two purposes. One is to slowly kill an opponent creature, the other is to kill one of your own creature in one turn in a sac deck. A 4/8 for 6f and 6 lands might be to expensive for a sacrifice, but the versatility and the ability to swallow a opponent creature make up for it. An alternative design would be to lower his price and allow only to swallow one of the owner’s creature.
The Phantasming Skywale is a mix between our beloved whale and mirror phantasm fitting both theme: Swallow and Transform. This one is definitly too strong and would need redesign as it kills AND copy one opponent’s creature. Alternative design could add a condition to allow the transformation like surviving a combat or collecting from opponent well.
Kodo Beast is a Warcraft 3 meme card and the idea that leads me to think to all these alternate swallow abilities. It is a slow removal card meant to collect while digesting opponent creature. I think it is too strong like this and I would redesign it to Gift - Swallow a creature with 3 or less attack as the value you can get from is too much right now.
The idea behind this Fearsome Look was to design another multi-tool card like the Emperor’s Command. No choice is meant to be strong, but the ability to choose one from is suppose to allow for a good card. It was design at a time where Swallow was everywhere but I think with the addition of more swallow card it would find a usefull place in the meta.
With the addition of many high land recquirement cards and a few land creation card, the rate at wich colors lands fill the board has increased. The Rain Maker is designed to mess with it. It can also help against rush deck and is also a late cheap collector.
Introduce the first possibility to get a card from the board to your hand. Would be perfect with a card like Aurora or Prophet of Tides or Mochi or the reposition anything without loosing collecting capability. Might be way too strong like this and need upping in faeria cost and land recquirement (I am thinking 4f, 3L).
A 3 wishes way of getting your health back. The 2 health of the structure means your creature will not stay trapped for too long. I like the idea that you choose the level of drawback from the card. It would synergize really well with high life creature with the ability to almost set you back to full life if needed.
