Some ideas for 'trump' cards:
4 Star Cost:
Beetle Swarm - 1 Attack 6 Hearts 4 Stars - Any damage instance dealt to any card or player is reduced to 1. This card can attack an additional time each of your turns. Once this card has destroyed three of your opponent's cards total, place a copy of it into play, but without this effect. (It still possesses its other effects.)
Predator Orca - 4 Attack 4 Hearts 4 Stars - This card can attack your opponent directly even while they have cards in their play area. At the end of each of your turns, banish this card. At the beginning of each of your turns, if this card was banished by its own effect, return it to your play area.
Mausoleum of the Dark Lord - 0 Attack 20 Hearts 4 Stars - This card cannot attack and does not prevent you from being attacked directly. At the start of your third turn after playing this card, destroy it and play any 'Dark Lord' card directly from your deck, without paying its Star cost.
Maiden Strife - 0 Attack 0 Hearts 4 Stars - Play up to three Maiden cards from your graveyard without paying their Star costs. Trigger their effects as though they were played from your hand. Additionally, they each gain 3 Attack and 3 Hearts. During your turn, you may pay 1 Star, banish this card from your graveyard, then search your deck for a Maiden creature card and add it to your hand, then shuffle your deck.
6 Star Cost:
Baleful Polymorph - 0 Attack 0 Hearts 6 Stars - Transform all cards your opponent has under their control into Helpless Sheep tokens. At the start of your opponent's second turn after you play this card, transform all surviving Helpless Sheep tokens back into their original forms.
-Helpless Sheep - 0 Attack 4 Hearts No Stars - Baaaaaaaah.
Four Seasons Maiden - 0 Attack 8 Hearts 6 Stars - At the start of each of your turns, you may choose one Maiden card in your graveyard with 0 Attack and 2 Hearts, banish it, then trigger its initial effect, or you may search your deck for a Maiden card that costs 2 Stars or less, and pay it after paying its Star cost, then shuffle your deck. This card cannot take more than 4 damage in a single turn.
Inhibitor Engine - 0 Attack 10 Hearts 6 Stars - Cards in your opponent's play area that cost 4 Stars or less to play do not possess any effects. This includes initial effects. This card cannot attack.
Challenger Knight - 6 Attack 8 Hearts 6 Stars - This card is the only card in your play area that is a valid attack target. You may only control one Challenger Knight at a time. Reduce all damage this card takes by 4. Your opponent can only declare an attack once per turn.
8 Star Cost:
Ultimate Firebase - 8 Attack 14 Hearts 8 Stars - This card cannot attack and deals no damage when it is attacked. At the start of each of your turns, deal damage equal to this card's Attack to up to three cards (of your choice) that your opponent controls, or your opponent themselves if they have no cards in play, bypassing all damage reduction and immunities. Once per turn, you may pay 2 Stars to trigger its start-of-turn effect an extra time. At the end of your turn, you may pay 8 Stars to inflict 100 damage to your opponent.
Divergent Reality - 0 Attack 0 Hearts 8 Stars - Create a second game that is a copy of the current match. Turns in the second game are resolved parallel to the turns in the initial game this card was played from. If you win in one game, you win in them both. Your opponent must win both games to be declared the winner, themselves.
Triumph Engine - 0 Attack 20 Hearts 8 Stars - This card cannot attack. At the start of each of your turns, place a Triumph counter on this card. If this card has three Triumph counters on it at the end of your opponent's turn, you win the game. This card cannot be removed from the play area except by damaging it until it is destroyed.
Rainbow Bridge - 0 Attack 10 Hearts 8 Stars - This card cannot attack and does not prevent you from being attacked directly. At the start of each of your turns, instead of drawing a card, you may choose a card your team has designed and add a copy of it to your hand. Reduce its Star cost by up to 2 if it has a conventional Star cost, or treat it as though it was played with 2 additional Stars spent if it has an X Star cost.
Yeah I'm not winning this one. The draw is not in my favor.
Hand is Invader Guardians, Invader Guardians, Beetle Brood, Fall Festival Maiden, Big Friendly Ghost, Nagalfar, Thorn Ward. I have 1 Star. My options aren't the best right now are they?