Omnath, you will be remembered, for better or for worse
Im not a fan of mulliganing to a Convoker your average hand (by this I mean a chance to cast a Convoker on turn three if you have it or happen to topdeck it) should be competitive against most of the decks in the format
When Gwenom attacks, you can cast the top card of your library that turn, and you can pay life instead of mana if you so desire
Whenever a permanent an opponent controls is put into a graveyard, put that card onto the battlefield under your control unless that opponent pays 3 life. Suddenly every lost permanent is a potential ally for you, and if not, your opponents have to lose life just to stop you from stealing their stuff
3 mana and 3 life for 3 cards is just a great rate, and the caveat of requiring 3 colors of mana was easy to fulfill between Battle lands and fetchlands
War Room allows to draw some cards by losing life, and its something that you can be interested in