This card works very well in Commander decks that dont let the mana empty from the mana pool, like Kruphix, God of Horizons, or cards that let you untap your permanents, like Seedborn Muse or Wilderness Reclamation
The unconditional and irreplaceable utility of Fierce Guardianship runs against that spirit of innovation, presenting players with all-purpose power they can no longer justify skipping over
Calgar being able to take tokens of all sorts and turn them into cards, or turn surplus mana back into more Space Marines is pretty decent at translating his acumen for eking all available advantage into victory
The deck starts by casting a number of powerful, efficiently-costed vampire creatures with strong secondary abilities including Clavileno (card draw, creature tokens), Cordial Vampire (+1/+1 counters), Drana (+1/+1 counters), Dusk Legion Duelist (card draw), Florian (filter/draw), Mavren Fein (vampire tokens), Nullpriest (lifelink, menace, reanimate), and many more