“Manticore of Darkness”’ effect can be activated during the End Phase when it was sent to the Graveyard from the field, hand, or your Deck that same turn.
When you send 1 “Manticore of Darkness” to the Graveyard to Special Summon another “Manticore of Darkness”, you can then send the new “Manticore of Darkness” to the Graveyard to Special Summon the first “Manticore of Darkness”.
If “Card of Safe Return” is active, and “Manticore of Darkness” is Special Summoned with its effect, you can draw a card. So with 2 “Manticores of Darkness”, 1 of them sent to the Graveyard, and “Card of Safe Return” in play, you can draw as many cards as you want.
When “Manticore of Darkness” is sent to the Graveyard because of hand size adjustment in the End Phase, you can activate its effect.
You can send a face-down Beast, Beast-Warrior, or Winged Beast-Type monster to the Graveyard for “Manticore of Darkness”’ effect.
Sending monsters to the Graveyard for “Manticore of Darkness”’ effect is a cost.
You can’t send a Monster Token to the Graveyard for “Manticore of Darkness”’ effect because Monster Tokens are taken off the field instead of going to the Graveyard.
The owner of “Manticore of Darkness” gets the effect, so if your opponent controls your “Manticore of Darkness” and it’s sent to the Graveyard, you get to activate the effect.
Netrep Rulings:
The effect of “Manticore of Darkness” will occur during either player’s End Phase.
Monster Tokens are not valid to satisfy the effect of “Manticore of Darkness.”
The effect of “Manticore of Darkness” activates in the Graveyard.
If two “Manticores of Darkness” are sent to the Graveyard in the same turn, one “Manticore of Darkness” will be Special Summoned to the Graveyard for each Beast Type, Winged Beast Type, or Beast Warrior Type sent to the Graveyard to satisfy the effect of “Manticore of Darkness.”
A “Manticore of Darkness” on the field may be sent to the Graveyard to Special Summon a “Manticore of Darkness” that was sent to the Graveyard that turn.“
“Necrovalley” does not negate the effect of “Manticore of Darkness.