combos:

felidar guardian + restoration angel = infinite ETB & LTB. (with felidar guardian on the battlefield, cast restoration angel. angel etbs targeting felidar guardian. felidar blinks, etbs targeting rest angel. rest angel is blinked, repeat as many times as you want.)

karmic guide + reveillark + viscera seer/ashnod's altar + infinite death triggers, infinite etb& ltb, infinite sac triggers, infinite scry (sac carmic guide to viscera seer, scry 1, then sac reveillark to viscera seer. when reveillark dies, it triggers and you target karmic guide to return it. when karmic guide ETBs, it targets and return reveillark, then viscera seer trigger 2 resolves. can sub viscera seer for ashnod's altar for infinite mana instead of scry.)

sun titan + fiend hunter + ashnod's altar = infinite colorless mana, infinite etb, infinite death. (with sun titan on the battlefield, play hunter and exile sun titan. sac fiend hunter to altar, adding 2m and returning sun titan. sun titan etb triggers, returns hunter, targeting sun titan. repeat.)